Russia says it is ordering troops back to base from the area near the border with Ukraine, apparently calling an end to a build-up of tens of thousands of soldiers that had alarmed the European Union.
The currencies of both Russia and Ukraine rose sharply after the announcement, signalling relief among investors just hours after Russia also ended war games in Crimea, the peninsula it occupied and annexed from Ukraine in 2014.
A pull-out of the troops brought in on top of the permanent contingent was likely to be welcomed by countries that had been expressing alarm at the prospect of further Russian intervention in eastern Ukraine.
Russian-backed separatists have been fighting the Ukrainian government in the region since 2014.
The Ukrainian president's spokeswoman said this month that Russia had more than 40,000 troops deployed on Ukraine's eastern border and about 40,000 in Crimea.
About 50,000 of them were new deployments, she said.
Russia has not provided any troop numbers.
In a tweet, President Volodymyr Zelenskiy said Ukraine "welcomes any steps to decrease the military presence & deescalate the situation in Donbas (eastern Ukraine)", adding "Grateful to international partners for their support".
Russian Defence Minister Sergei Shoigu said he had ordered troops involved in exercises to return to their bases by May 1 as they had completed what he called an "inspection" in the border area.
"I believe the objectives of the snap inspection have been fully achieved. The troops have demonstrated their ability to provide a credible defence for the country," Shoigu said.
Military hardware was to be left at a training ground near the city of Voronezh, about six hours' drive from Ukraine, so that it could be used again later this year in another big scheduled exercise.