President Petro Poroshenko said on September 8 that pro-Russian separatists have so far handed over about 1,200 prisoners-of-war to the Ukrainian side under the terms of a ceasefire agreement.
The two sides are meant to exchange all their POWs under the terms of the cease-fire deal, clinched on September 5.
Poroshenko was speaking during a visit to Mariupol, a port city in the east of Ukraine which the rebels advanced towards last week before the ceasefire took effect.
Poroshenko also said he has ordered reinforced defense of Mariupol with tanks, rocket launchers, and aerial defense.
Despite the truce, Ukrainian troops have come under fire from pro-Russian rebels on the eastern edge of Mariupol.
Later on September 8,
the Kremlin said Russian President Vladimir Putin spoke by telephone with Poroshenko about how to reach a peaceful resolution to the crisis.
In a statement, the Kremlin press service said: "The two presidents continued discussing steps that would facilitate the peaceful settlement of the situation in southeastern Ukraine," and that "the dialogue will be continued."
Based on reporting by Reuters, RFE/RL, AFP, BBC, and Interfax