Ukraine is preparing to withdraw heavy weaponry away from separatist rebel lines in the east, the military says.
The two sides agreed on Saturday to set up a buffer zone in eastern Ukraine, more than a fortnight after a ceasefire came into force.
Although the truce is still in place, clashes have continued around the cities of Donetsk and Mariupol.
More than 3,000 people have died since fighting broke out in the two regions of Donetsk and Luhansk in April.
Under the terms of the nine-point deal agreed in Belarus, both the pro-Russian rebels and Ukrainian forces are to pull back their heavy artillery 15km (9.5 miles) from the line of engagement, creating a 30km buffer zone.
Military aircraft are banned from flying over the conflict zone and “foreign mercenaries” are to be withdrawn on both sides.
Ukrainian National Security and Defence Council spokesman Col Andriy Lysenko said pro-Russian rebels had on their part begun pulling back their heavy artillery, but it was “not as massive as we expected”.
He added that two servicemen had been killed in the past day.
