Russian President Petro Poroshenko agreed to the ceasefire after Ukraine accused Russia of sending troops and arms onto its territory in support of the separatists, who had suffered big losses over the summer, but Moscow denies sending troops or arming the rebels, according to The Associated Press.

Ukraine, Russia and the Kremlin-backed separatists signed the cease-fire deal in the Belarusian capital Minsk on Friday in an effort to end more than four months of bloodshed in the region, the AP reported.

The negotiators also agreed on the withdrawal of all heavy weaponry, the release of all prisoners and the delivery of humanitarian aid to devastated cities in eastern Ukraine, according to the AP.

Although the ceasefire had mostly held during Saturday, citizens in the other main flashpoint, the rebel-held industrial city of Donetsk, complained of sporadic shelling and gunfire, especially near the airport, which remains in government hands, the AP reported.

Western leaders voiced skepticism over Russia's commitment to the deal, according to the AP. A previous 10-day ceasefire, which each side repeatedly accused the other of violating, yielded few results at the negotiating table.

"The ceasefire is looking good for now but we know they (the Ukrainian side) are only using it to bring in more forces here and ammunition and then to hit us with renewed strength," said one rebel commander in Donetsk known by his nickname Montana, according to the AP.

Andriy Lysenko, the spokesman of Ukraine's National Security and Defence Council, said Kiev wanted the exchange of prisoners of war to take place "as fast as possible" but gave no timeframe, the AP reported. He said the rebels were holding more than 200 Ukrainians captive.

Poroshenko spent Thursday and Friday at a NATO summit in Wales, at which President Barack Obama and other leaders urged Russian President Vladimir Putin to pull its forces out of Ukraine, according to the AP. NATO also approved wide-ranging plans to boost its defenses in eastern Europe in response to the Ukraine crisis.

The airport in Donetsk has been under the control of government troops since May and has come under unremitting attacks from pro-Russia separatist rebels since then.