Hundreds of thousands of union members and labour activists have rallied around the world to mark May Day.
The tradition of May Day marches for workers’ rights began in the United States in the 1880s and quickly spread to other countries at a time when industrialisation pitted poorly paid employees against increasingly dominant factory employers and landowners.
Over the decades, the May Day protests have also become an opportunity to air general economic grievances or political demands.
Demonstrations took place in major cities stretching from Paris to St Petersburg, from Hong Kong to Johannesburg.
May Day rallies were also being held in parts of Asia, including the Philippines, Malaysia, Indonesia, Taiwan, Cambodia and Myanmar.
In St Petersburg, Russia the demonstration soon turned ugly when riot police moved into break it up shortly before the marchers set off.
More than 60 supporters of opposition leader Alexei Navalny were arrested.
Some of them carried signs saying "Putin is not immortal," in reference to Russian President Vladimir Putin.
French authorities announced tight security measures for May Day demonstrations, with Christophe Castaner, the interior minister, saying there was a risk that "radical activists" could join anti-government yellow vest protesters and union workers in the streets of Paris and across the country.
More than 7,400 police were deployed, aided by drones to give them an overview of the protests and a quicker way to head off potential violence.
Protesters in Seoul, South Korea rallied in streets near City Hall, marching under banners denouncing deteriorating working conditions and calling for equal treatment and pay for non-regular workers.
Labourers in Jakarta, the capital on Indonesia, gathered at national monuments and other places, shouting their demands.
"We demand the rights of workers and their families," said Joko Harianto, head of the national trade union.
"People think things are good, but actually these rights are very difficult to obtain."
Two protesters and a police officer were injured in the Italian city of Turin when police blocked a demonstration against the construction of a high-speed rail line between France and Italy, according to ANSA, an Italian news agency.
Meanwhile, union rallies in Greece paralysed national rail, island ferry and other transport services.
Hundreds of people gathered in central Athens on Wednesday for three separate marches to parliament organised by rival unions and left-wing groups.
Spain's workers marched in its major cities to make their voices heard days before acting Prime Minister Pedro Sánchez starts negotiating with other parties to form a new government.
Unions are pressing Sánchez to roll back business-friendly labour and fiscal reforms that have remained in place since the conservatives were in charge.
In Germany, the country's biggest trade union urged voters to participate in this month's European Parliament election and reject nationalism and right-wing populism.
The DGB, a confederation of unions with almost 6 million members, warned that the political and economic turmoil in Britain following its vote to leave the European Union "shows what happens if those who stoke fear but have no plan for the future gain the upper hand".
An opposition party in South Africa used May Day to rally voters a week before the country's national election.
Economic Freedom Fighters members, wearing their signature red shirts and berets, gathered at a stadium in Johannesburg to cheer populist stances that have put pressure on the ruling African National Congress to address topics like economic inequality and land reform.
Protesters threw cobblestones and fireworks at police, included mounted officers, who were trying to keep them away from a neo-Nazi rally in Gothenburg, Sweden's second largest city.
In neighbouring Denmark, helmeted police circled their vans around hooded people in black shouting anti-police slogans to keep them away from other May Day demonstrations in Copenhagen, the capital.