CHERNIHIV REGION, Ukraine — Russia and Ukraine began their largest exchange of prisoners of war Friday, with each side returning 390 soldiers and civilians, according to both governments. More swaps were expected Saturday and Sunday, as the two countries have committed to exchange 1,000 prisoners each.

“We are bringing our people home. The first part of the agreement to exchange 1000 for 1000 has been implemented,” President Volodymyr Zelenskyy of Ukraine wrote in a post on social media.

He included pictures of Ukrainians who had been returned, most of them men with shaven heads and gaunt frames, their shoulders draped in Ukrainian flags.

Russia’s Defense Ministry said 270 of its troops and 120 civilians had been turned over in Belarus, before being transported to Russia. Ukraine’s military leadership said the same figures applied to the Ukrainians who were returned.

The exchange was agreed upon at negotiations in Istanbul last week, the first time the two sides have engaged in direct talks since the early months of the war.

On Friday, hundreds of families gathered at a site in the northeastern Chernihiv region of Ukraine to wait for the arrival of buses carrying freed service members to a hospital where doctors looked them over.

Families cheered and shouted the names of those they hoped were on the buses, pleading for information.

A young woman sobbed inconsolably when her husband failed to emerge.