Thousands of activists are attending a May Day rally in honour of veteran political campaigner Tony Benn and rail union leader Bob Crow who died within days of each other last month.
The traditional May Day event in London, which celebrates workers' achievements, will honour the two men, who died within a few days of each other earlier this year.
Tony Lennon, chief steward of the London May Day Organising Committee, said: "This year's London May Day presents a huge opportunity for the trade unions and the community to both pay tribute to the massive contribution made by Bob Crow and Tony Benn to the fight for workers' rights, and to send out a clear message that the battle goes on."
Mick Cash, acting general secretary of the Rail, Maritime and Transport (RMT) union, said: "RMT branches and regions have been building for a massive turnout on May Day in London in memory of both Bob Crow and Tony Benn under the theme: Don't Mourn - Organise."
In pictures: May Day 2014 protests
In pictures: May Day 2014 protests
Members of Indonesian Labour unions and labour activists march on a street in the central business district in Jakarta
A member of an Indonesian Labour union waves a flag in Jakarta
Indonesian labour activists representing underpaid and downtrodden workers perform during a Labour Day protest in Jakarta
A Femen activist bearing the slogan "Fascist Epidemic" on her chest shouts slogans as she protests against France's far-right National Front (FN) during the party's May Day rally in Paris
Protesters chant slogans during a May Day rally in front of the Petronas Twin Towers in Kuala Lumpur. Malaysia's opposition and activists demonstrate on May Day, also known as Labour Day, against the rising cost of living due to reduced subsidies and increased taxes
Thai laborers with national flags march to mark International May Day at Royal Plaza in Bangkok. Thousands of Thai laborers rally on Labor Day calling on the government to improve the standards of their work and living conditions
Riot police use water cannon to disperse protesters during a May Day demonstration in Istanbul
Riot police fires tear gas to push back protesters during a May Day demonstration in Istanbul. Turkish police fired water cannon and tear gas to prevent hundreds of protesters from defying a ban on May Day rallies and reaching Istanbul's central Taksim Square
Activists around the world are marking International Worker's Day. May 1st has traditionally been a flash-point date that has seen clashes between police and protesters. In Turkey clashes have erupted in Istanbul between May Day demonstrators and riot police as crowds determined to defy a government ban tried to march to the city's famous Taksim Square.
Security forces pushed back demonstrators with water cannons and tear gas. Protesters retaliated by throwing objects at police.
In Cambodia, witnesses said civilian auxiliary police, armed with clubs and often used by the government to break up protests, turned on the demonstrators after opposition leaders spoke to the crowd and left the rally site.
The assaults appeared to be random and limited, and were over in less than an hour.
In Moscow, about 100,000 people marched through Red Square, the first time the annual parade has been held on the vast cobblestoned square outside the Kremlin since the fall of the Soviet Union in 1991.
Marchers held up signs saying "Let's go to Crimea for vacation" and "Putin is right." Russian flags fluttered through the crowd.
Thousands of Malaysians held a peaceful protest in downtown Kuala Lumpur against a looming goods and services tax that they fear will increase the cost of living.