More than a million people took part in rallies across Russia, with the largest crowds attending demonstrations sponsored by the authorities and pro-Kremlin parties.
In Berlin, tens of thousands of German trade unionists attended demonstrations urging the government not to cut social benefits.
In Stockholm, Swedish police took about 130 people into custody after a May Day rally turned violent, with demonstrators smashing shop windows.
in London, British trade unionists held the traditional rally in Trafalgar Square, this year protesting peacefully against job and pension cuts.
In the Belarus capital Minsk, around 1,000 people called for the release of opposition leader Alyaksandr Milinkevich.
Turkish police detained a total of 85 people during May Day demonstrations across Turkey. In Istanbul, violence broke out when police broke up an unsanctioned rally.
Earlier, numerous rallies were held in countries across Asia. In Tokyo, a crowd of more than 40,000 Japanese protested growing social inequality between the rich and the poor.
(compiled from agency reports)