Tens of thousands of people have marched in Moscow and other Russian cities to celebrate May Day.
Trade unionists organized a march that drew some 25,000 people in the Russian capital, where police were deployed to prevent violence.
Communist supporters held a separate rally, shouting anti-government slogans and carrying pictures of Stalin.
In Belarus, opposition supporters marched in the capital Minsk to protest the arrests of opposition party leaders. One of the rally's organizers, former President Stanislav Shushkevich, was summoned to speak with authorities about the march.
Police in the Turkish city of Istanbul detained at least 20 people taking part in a banned rally.
In Indonesia, thousands of police patrolled the streets of Jakarta to guard against a repeat of May Day riots in 2001. Organizers called today's rally to demand better working conditions and protest planned revisions to a 2003 labor law.
In Cambodia, police briefly detained a union leader Chea Mony after a demonstration in Phnom Penh. May Day rallies also were held in Jakarta and Tokyo.
Some information for this report was provided by AFP and AP.