President Petro Poroshenko says the Ukrainian troops are making an “organized” withdrawal from the embattled town of Debaltseve.
Petro Poroshenko said 80% of Ukraine’s forces had left on Wednesday morning, February 18, with more to follow.
Fighting has raged over the transport hub, with pro-Russian rebels seizing control of most areas, despite a ceasefire deal.
Russia’s foreign minister said Ukrainian forces had been encircled and were forced to battle their way out.
“I’m reckoning that common sense will prevail,” said Sergei Lavrov as he urged the rebels to provide troops who surrendered with food and clothes.
Earlier, Vice-President Joe Biden accused Russia of violating the accord, agreed in Minsk last week.
Eyewitnesses saw dozens of tanks and columns of weary Ukrainian troops retreating from Debaltseve on February 18.
“This morning the Ukrainian armed forces together with the National Guard completed an operation for a planned and organized withdrawal from Debaltseve,” the Ukrainian president said in a statement before travelling to the frontline in the east.
“As of now we can say that 80% of our units have left,” he said.
“We are expecting another two columns [to leave].”
The withdrawal comes after Russian President Vladimir Putin urged Ukraine’s troops in Debaltseve to surrender.
International observers monitoring the truce have been unable to enter the town.
It has become a key prize for rebels and government forces, as it sits on a strategic railway line linking rebel-held Donetsk and Luhansk.
Most of its 25,000 population has been evacuated but about 7,000 civilians are still believed trapped by the fighting.
The ceasefire, which came into effect on February 15, has been broadly observed elsewhere.
Rebel leaders in the so-called Donetsk People’s Republic said on February 18 they had begun to withdraw heavy weaponry from the parts of the frontline where the ceasefire was holding.
The withdrawal was due to start no later than the second day after the truce came into effect and be completed within two weeks, creating buffer zones 30-85 miles wide.
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