Western ambassadors watched May Day ceremonies in the Soviet capital for the first time in nine years, ending a boycott that followed the Soviet military drive into Afghanistan.
Elsewhere, thousands of people attended rallies and parades on the day honoring workers of the world.In Europe, security forces clashed with demonstrators in Poland, and arrests were reported in East Berlin and Turkey.
In Latin America, protesters threw sticks of dynamite at four buildings in Peru, burned effigies of President Reagan in Honduras and were dispersed by tear gas and water cannons in Chile.
Troops also fired at marchers in the Philippines.
In Moscow's Red Square, hundreds of thousands of people toted banners extolling "perestroika" (economic restructuring), "glasnost" (openness) and other Communist Party programs.
One sign called for good superpower relations and depicted a handshake, the U.S. and Soviet flags, and the inscription "Da!" (Yes). In past years, some May Day floats denounced the United States.
Jack Matlock made the first May Day appearance by a U.S. ambassador since the Soviets intervened in Afghanistan in 1979 to aid a pro-Moscow government.
"I'm here today first of all because it is not a military-oriented holiday, and because agreements have been signed for the Soviet withdrawal from Afghanistan," Matlock said. "Also, our president is due in less than a month" for his fourth summit meeting with Mikhail S. Gorbachev.
The West German envoy, Andreas Meyer-Landrut, said it was the first time ambassadors from all 12 Common Market countries attended May Day festivities since 1979.
In Poland, thousands of people demonstrated in at least 15 cities across the nation, heeding a call by the Solidarity labor federation for a national "day of protest" against price increases and restriction of union activities. Scores of people were detained and several people were injured in clashes with police.
Turkish authorities detained more than 100 people who tried to mark May Day in Istanbul and Ankara, the Anatolia news agency said.
Police rounded up half a dozen dissidents during the May Day parade in communist East Berlin, including one who had chained himself to a cross outside a church.
In the Philippines, troops shot at May Day marchers south of Manila. Organizers claimed the soldiers fired "without provocation" into a crowd, wounding two people. Police said they opened fire while chasing two suspected members of a communist assassination team.
Militant South African trade unions, barred from holding outdoor rallies, held indoor meetings to celebrate May Day and protest the government's clampdown on the black labor movement.
Tens of thousands of workers in Santiago, Chile, gathered at a rally called by the National Workers Commands, the country's largest dissident labor federation. A 16-year-old youth was wounded by a gunshot as police scattered demonstrators who tried to march downtown to protest the military government. Some protesters were detained, but police gave no figure.
Demonstrators in Honduras burned effigies of Reagan and Honduran President Jose Azcona Hoyo. Newspapers estimated 30,000 took part in rallies in six cities.
In Lima, Peru, demonstrators linked to the anti-government guerrillas threw sticks of dynamite at two banks and two other buildings during a May Day march through the capital. No one was reported hurt.
In Managua, Nicaragua, President Daniel Ortega told a holiday rally that troops would launch their biggest offensive ever against rebels if they did not agree to extend a 60-day cease fire. A two-month cease-fire began April 1.