Twenty people who had been held captive in two breakaway regions were handed to the government, Kiev said.

Separatists took back 14 prisoners but three others refused to return, Ukrainian President Volodymyr Zelensky's office told AFP.

"I'm happy every time we get our citizens back: our heroes, soldiers, political prisoners and ordinary citizens of Ukraine," Zelensky said in a video address.

"We will fight until all Ukrainians come home."

Ukraine's commissioner for human rights, Lyudmyla Denisova, said the quarantine imposed in Ukraine to control the coronavirus pandemic had made prisoner exchange talks "much harder".

The prisoners will undergo the mandatory quarantine, she said on Facebook.

"The humanitarian value of the release of people detained in time of conflict cannot be underestimated," the International Committee of the Red Cross said in a statement.

"It is also essential that, even in the time of COVID-19, detainees continue to be released and are able to finally see their families again."

The Ukrainian presidency announced the swap deal last week, promising to complete it before Orthodox Easter on Sunday.

Ties between Ukraine and Russia were shredded after the bloody 2014 uprising ousted a Kremlin-backed government in Kiev.

Russia went on to annex Crimea and support insurgents in eastern Ukraine, who launched a bid for independence in 2014. Since then, more than 13,000 people have been killed in the conflict.