(Photo by Eduard Korniyenko/Reuters)

People walk with flags and banners at Red Square during a May Day rally in Moscow May 1, 2015. The placard reads, “Let's turn Moscow into a comfortable and safe city”. (Photo by Maxim Zmeyev/Reuters)

Supporters of Russia's Communist party sing as they take part in a May Day rally in Moscow May 1, 2015. International Workers' Day, also known as Labour Day or May Day, commemorates the struggle of workers in industrialised countries in the 19th century for better working conditions. (Photo by Maxim Shemetov/Reuters)

A Pakistani woman shouts slogans at a rally to observe the Labor Day in Peshawar, Pakistan, Friday, May 1, 2015. Pakistan observed International Labor Day with other nations worldwide. (Photo by Mohammad Sajjad/AP Photo)

A man holds a banner with an image depicting Brazil's President Dilma Rousseff during a rally to commemorate International Workers' Day, in Sao Paulo May 1, 2015. (Photo by Nacho Doce/Reuters)

An opposition demonstrator, her face painted with the colors of the Venezuelan national flag and the word “Freedom” on her forehead, participates in the May Day march in Caracas, Venezuela, Friday, May 1, 2015. Pro-government and opposition workers marched today in the midst of the political and economic crisis prevailing in the country, with separate marches that took place to mark International Workers Day also known as May Day. (Photo by Ariana Cubillos/AP Photo)

An opposition demonstrator with a Venezuelan national flag draped around her shoulders, holds a sigh with a message that reads in Spanish; “Son, I keep fighting for Venezuela, so that you don't leave it, or sink with it”, during a May Day march in Caracas, Venezuela, Friday, May 1, 2015. (Photo by Ariana Cubillos/AP Photo)

Venezuela's first lady Cilia Flores wears a jacket made in the colors of Venezuela's flag during a May Day rally in Caracas, Venezuela, Friday, May 1, 2015. Flores' jacket reads her name, along with her official title “Primera Combatiente”. Instead of first lady, Flores' goes by the title “First Fighter”. (Photo by Fernando Llano/AP Photo)

A supporter of Venezuela's President Nicolas Maduro attends a rally from her window to celebrate May Day in Caracas May 1, 2015. (Photo by Jorge Silva/Reuters)

A child plays with a colored ribbon during a visit to Tiananmen Square in Beijing, Friday, May 1, 2015. (Photo by Ng Han Guan/AP Photo)

Workers shout slogans as they march on the street during May Day, in Pamplona northern Spain, Friday, May 1, 2015. Tens of thousands of workers marked May Day in European cities with a mix of anger and gloom over austerity measures imposed by leaders trying to contain the eurozone's intractable debt crisis. (Photo by Alvaro Barrientos/AP Photo)

Demonstrators of the General Confederation of Work (CGT) lay down a giant flag during May Day celebrations in Valencia, Spain, May 1, 2015. (Photo by Heino Kalis/Reuters)

A supporter of the Iraqi Communist Party takes part in a May Day celebration in Baghdad, Iraq, Friday, May 1, 2015. (Photo by Hadi Mizban/AP Photo)

Supporters of the Iraqi Communist Party take part in a May Day celebration in Baghdad, Iraq, Friday, May 1, 2015. May 1 is celebrated as the International Labor Day or May Day across the world. (Photo by Hadi Mizban/AP Photo)

People hold placards during a May Day rally in Jakarta, Indonesia, May 1, 2015. Thousands of workers urged the government to raise minimum wages and improve working condition, according to local media. (Photo by Reuters/Beawiharta)

Policemen stand guard in front of the Presidential palace as workers hold a protest during a May Day rally in Jakarta, Indonesia, May 1, 2015. (Photo by Reuters/Beawiharta)

Thousands of Indonesian workers march during a May Day rally in Jakarta, May 1, 2015. (Photo by Reuters/Beawiharta)

A demonstrator sports a tattoo showing the symbol of the Italian Communist party during a protest against the Expo 2015 fair in Milan, Italy, Friday, May 1, 2015. (Photo by Luca Bruno/AP Photo)

People throw smoke grenades during the annual Labour Day protest in front of Presidential Office in Taipei, Taiwan, May 1, 2015. Thousands of people marched to demand higher wages and labour rights, according to local media. The head banner reads, “shorten working hours; no overfatigue”. (Photo by Patrick Lin/Reuters)

A member of a brass band plays an instrument during a rally to mark May Day in Gauhati, India, Friday, May 1, 2015. May 1 is celebrated as the International Labor Day or May Day across the world. (Photo by Anupam Nath/AP Photo)

Demonstrators participate in May Day protests at City Hall in San Francisco, California May 1, 2015. (Photo by Robert Galbraith/Reuters)

A man holds up signs during a May Day protest in San Francisco, California May 1, 2015. (Photo by Robert Galbraith/Reuters)

Demonstrators participate in May Day protests in Los Angeles, California May 1, 2015. (Photo by Mario Anzuoni/Reuters)

Workers march holding umbrellas marked with palm prints, symbolizing clean hands, free of corruption, during a May Day parade in a show of support for Ecuador's President Rafael Correa, in Quito, Ecuador, Friday, May 1, 2015. (Photo by Dolores Ochoa/AP Photo)

Women march hand in hand as they take part in the May Day parade, in Quito, Ecuador, Friday, May 1, 2015. Left-wing groups, governments and trade unions were staging rallies around the world Friday to mark International Workers Day, also known as May Day. (AP Photo/Dolores Ochoa

Confetti litters the parade route as workers take part in the May Day parade in Quito, Ecuador, Friday, May 1, 2015. (Photo by Dolores Ochoa/AP Photo)

A small group of Bahraini women, carrying national flags and a banner supporting political prisoners, march quickly between police patrols, on the lookout for violators of a protest ban, in Manama, Bahrain, Friday, May 1, 2015. The government denied permission for Labor Day protests, so protesters in several opposition areas went out in small groups for quick marches between police patrols. The banner reads: “Revolution of Chains, in solidarity with Jaw central prison inmates”. (Photo by Hasan Jamali/AP Photo)

Bahraini anti-government protesters hold up posters calling for freedom for jailed doctors, rear, and engineers, foreground, in Manama, Bahrain, Friday, May 1, 2015. The front poster reads: “Imprisoned Engineers! Destroying tyranny and building nations”. (Photo by Hasan Jamali/AP Photo)

A man entertains with a traditional musical instrument during a Labour Day rally in Lagos on May 1, 2015. Tens of thousands of people across the globe were hitting the streets on May 1 for mass rallies marking International Labour Day. (Photo by Pius Utomi Ekpei/AFP Photo)

A protester wearing a toy British police helmet and an Anonymous mask takes a picture during a rally at the end of a May Day demonstration march in Trafalgar Square in London, Friday, May 1, 2015. Tens of thousands of workers marked May Day in European cities with a mix of anger and gloom over austerity measures imposed by leaders trying to contain the eurozone's intractable debt crisis. (Photo by Matt Dunham/AP Photo)

Masked protestors are seen in front of a banner, which reads “Class against Class” during a May Day march in Hamburg, Germany, May 1, 2015. (Photo by Fabian Bimmer/Reuters)

People walk during a May Day march through Berlin's Kreuzberg district, Germany, May 1, 2015. (Photo by Hannibal Hanschke/Reuters)

In this May 1, 2015 photo riot police officers walk pass flares during a May Day demonstration in Hamburg, Germany. (Photo by Markus Scholz/AP Photo/DPA)

Police arrest two demonstrators during clashes at a May Day march in Hamburg, Germany, May 1, 2015. (Photo by Fabian Bimmer/Reuters)

A man walks in the street of Okmeydani neighborhood of Istanbul, Turkey, May 1, 2015

Protesters from the Communist-affiliated trade union PAME hold red flags during a May Day rally in front of the parliament building in Athens May 1, 2015. (Photo by AlkisKonstantinidis/Reuters)

A man wearing a carnation at his lapel reads a newspaper during a May Day rally in front of the parliament building in Athens May 1, 2015. (Photo by AlkisKonstantinidis/Reuters)

A demonstrator throw a firebomb during clashes with Turkish riot police officers in Istanbul, Turkey, Friday, May 1, 2015. (Photo by Emrah Gurel/AP Photo)

Portuguese Maria da Luz, 88, wearing a red carnation on her coat, shouts slogans during a march marking the international May Day, in Lisbon, Friday, May 1, 2015. A red carnation is the symbol of the revolution that restored the democracy in Portugal in 1974. (Photo by Francisco Seco/AP Photo)

Workers shout slogans against austerity measures during a march by the Portuguese union CGTP in Lisbon May 1, 2015. (Photo by Hugo Correia/Reuters)

A man walks past smoke left by tear gas during clashes against police on Labor Day in Bogota, Colombia May 1, 2015. (Photo by Jose Miguel Gomez/Reuters)

A man shouts slogans during protests for Labor Day in Bogota, Colombia May 1, 2015. International Workers' Day, also known as Labour Day or May Day, commemorates the struggle of workers in industrialised countries in the 19th century for better working conditions. (Photo by Jose Miguel Gomez/Reuters)

A demonstrator walks in front riot policemen during protests for Labor Day in Bogota, Colombia May 1, 2015. (Photo by Jose Miguel Gomez/Reuters)

Cuban army cadets react to the photographer as they march in Revolution Square marking May Day, in Havana, Cuba, Friday, May 1, 2015. (Photo by Ramon Espinosa/AP Photo)

A woman dressed in a skirt with a picture of the revolutionary hero Ernesto “Che” Guevara marches during a May Day parade in Havana May 1, 2015. International Workers' Day, also known as Labour Day or May Day, commemorates the struggle of workers in industrialised countries in the 19th century for better working conditions. (Photo by Enrique De La Osa/Reuters)

A Cuban Navy soldier carries a child on his shoulders as they march in Revolution Square marking May Day, in Havana, Cuba, Friday, May 1, 2015. Thousands of people converged on the plaza for the traditional march, led this year by President Raul Castro and Venezuelan President Nicolas Maduro. (Photo by Ramon Espinosa/AP Photo)

A woman holds up a handwritten sign against the U.S embargo during a march in Revolution Square marking May Day, in Havana, Cuba, Friday, May 1, 2015. (Photo by Ramon Espinosa/AP Photo)

Demonstrators take part during a march for Labour Day in Mexico City May 1, 2015. (Photo by Edgard Garrido/Reuters)

Protesters wearing Guy Fawkes masks take part in a march for Labor Day in Mexico City May 1, 2015. (Photo by Edgard Garrido/Reuters)

An indigenous woman and her daughter look at a march for Labor Day in Mexico City May 1, 2015. (Photo by Edgard Garrido/Reuters)

A supporter of Russia's Communist party attends a May Day rally in Moscow May 1, 2015. (Photo by Maxim Shemetov/Reuters)

Communists carry a poster depicting U.S. President Barack Obama during a traditional May Day march in St.Petersburg, Russia, Friday, May 1, 2015. (Photo by Dmitry Lovetsky/AP Photo)

Participants in a May Day rally carry flags in front of the state Capitol in Denver, Friday, May 1, 2015. (Photo by Brennan Linsley/AP Photo)

Demonstrators participate in May Day protests in San Francisco, California May 1, 2015. (Photo by Robert Galbraith/Reuters)