Turkish police fired tear gas and water cannon to disperse May Day protesters in Istanbul on Thursday, as millions took to the streets around the world to mark International Labour Day.
About 100,000 workers paraded on Moscow's iconic Red Square for the first time since the 1991 collapse of the Soviet Union as the annexation of Crimea triggered a surge of patriotism.
Protesters were also out in force in European countries including France, Italy and Greece, marching against unemployment and austerity policies. Across Asia, workers took to the streets demanding better working conditions and salary hikes.
In tense Istanbul, hundreds of riot police backed up by water cannon moved in on protesters as they tried to breach the barricades leading up to the symbolic Taksim square on the anniversary of clashes that spawned a nationwide protest movement.
At least 51 people were injured and 138 detained across the city, the Progressive Lawyers Association said, as police clashed with flag-waving and balaclava-wearing protesters hurling stones and Molotov cocktails.
In Istanbul's Besiktas, Mahmut Tanal, a lawmaker from the main opposition Republican People's Party was beaten by police who tried to pushed him away from a water cannon truck.
"This is a picture that you can only see in countries which are governed by dictator regimes," Tanal told AFP.
In Turkey's capital Ankara, police fired volleys of tear gas and jets of water on hundreds of protesters trying to march to the Kizilay Square, also declared off limits.
The most impressive May Day turnout was in Russia, where a huge column of demonstrators waving Russian flags and balloons marched through Moscow's iconic square near the Kremlin and voiced their support for President Vladimir Putin and his hardline stance on the Ukraine crisis.
"Putin is right", "Proud of the country" and "Let's support decisions of our president" read the banners carried by the smiling demonstrators, a colourful spectacle harking back to Soviet times.
May Day was a key date in the Soviet calendar, but in recent years, the annual demonstrations have been relegated to a city highway.
Trade union leaders said about two million people had turned up for May Day rallies across Russia.
The tone was markedly different in Greece where thousands marched in the countries two main cities of Athens and Salonika against an austerity drive following a disastrous debt crisis that led to mass lay-offs.
In Italy's Turin, scuffles broke out between police and hundreds of protesters.
Activists lobbed smoke bombs at police, who charged demonstrators in the northern industrial city, which has been badly hit by a painful two-year recession.
Thousands marched in France with the biggest rallies in Paris and other major cities such as Bordeaux and Toulouse targeting the Socialist government's budget cuts to rein in the deficit.
Rallies also took place across Asia, including in Hong Kong, Jakarta, Kuala Lumpur, Singapore and Taipei.
In Cambodia, security forces armed with sticks and batons forcibly dispersed dozens of May Day protesters near Phnom Penh's Freedom Park, according to an AFP photographer. Several people were beaten.
In Indonesia, protestors carrying portraits of leftist idols such as Che Guevara, Fidel Castro and the country's first president Sukarno, marched to the state palace in Jakarta.
Some sang and danced as others carried a three-metre-long toy octopus wearing a red hat with the words "Capitalist Octopus, Sucking the Blood of Workers."
More than 1,000 protesters gathered in Hong Kong's landmark Victoria Park to walk towards the government headquarters waving colourful flags and placards, while singing a Chinese version of "Do You Hear the People Sing?" from the musical Les Miserables, while calling for better working conditions and wages.
Domestic helper rights concern groups, which made up a large portion of the rally, wore masks with a picture of Erwiana Sulistyaningsih, an Indonesian maid who was allegedly abused by her employer for months, while shouting: "We are workers, we are not slaves".
About 20,000 people rallied in Kuala Lumpur against price hikes implemented by Malaysia's long-ruling government, which already is under domestic and international scrutiny over its handling of the passenger jet that disappeared on March 8.
More than 10,000 workers marched to the labour ministry in Taiwan's capital Taipei demanding wage hikes and a ban on companies hiring cheap temporary or part-time workers.
In Singapore, a protest organised by critics of the government's immigration policy drew around 400 protestors chanting slogans calling for the long-ruling People's Action Party to step down.