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Peter Leonard, Associated Press
Pro-Russia rebels, one of them holding a flag of the rebel-held city of Luhansk, pose for a photo in Debaltseve, eastern Ukraine on Thursday, Feb. 19, 2015. After weeks of relentless fighting, the embattled Ukrainian rail hub of Debaltseve fell Wednesday to Russia-backed separatists, who hoisted a flag in triumph over the town. The Ukrainian president confirmed that he had ordered troops to pull out and the rebels reported taking hundreds of soldiers captive.

DEBALTSEVE, Ukraine — Rebel fighters, many of them Cossacks, roamed the streets of Debaltseve on Thursday, a day after Ukrainian forces began withdrawing from the besieged town. The mood was celebratory, with fighters laughing, hugging each other and posing for photos.

Associated Press journalists drove Thursday around half of the town that has been a focal point for weeks of fierce fighting in eastern Ukraine, finding all its neighborhoods under the control of rebel fighters.

Nikolai Kozitsyn, a Russian Cossack leader and prominent warlord in separatist eastern Ukraine, drove around in a Humvee-like vehicle that had been captured from Ukrainian troops. Other rebels were seen waving separatist flags.

All around lay the wrecked remains of Ukrainian armored vehicles. A government encampment near a crossroads lay deserted and rebel fighters searched through its bunkers and abandoned tents, looking to salvage equipment and clothing left behind.

Two fighters inspected a tank left behind by Ukrainians that they described as a "gift" from the government troops. They then grabbed a bloodied blue-and-yellow Ukrainian flag lying next to the tank and ground it into the frozen earth with their boots.

But in a reminder of the dangers of the area, one car carrying Cossacks hit a land mine 200 meters (yards) from the AP journalists, killing one Cossack and injuring one other.

On debris-littered streets in devastated residential areas, civilians milled about. Some thanked the rebel fighters.

Ukrainian troops began abandoning Debaltseve on Wednesday after weeks of heavy fighting. A Ukrainian military spokesman said Thursday that more than 90 percent of its forces have been withdrawn from Debaltseve and its surroundings, but left unclear when the retreat might be completed.

The town is significant for the rebels because it's a railway junction that straddles the most direct route between Donetsk and Luhansk, the separatist region's two main cities. However, Ukrainian military spokesman Andriy Lysenko said Thursday the three-week siege had left the town's infrastructure in ruins.

"A strategic rail hub has stopped its existence the way it was," he said in the Ukrainian capital of Kiev.

A statement from Ukraine's military general staff said 13 soldiers were killed and 157 wounded by artillery fire during the withdrawal. More than 90 soldiers were taken prisoner during the battle for Debaltseve and the whereabouts of 82 others are unclear, it said.

Dozens of Ukrainian military vehicles could be seen retreating Thursday from Debaltseve to the government-held town of Artemivsk. Many of them were riddled with bullet holes or had their windshields destroyed.

"We left under heavy fire, driving on small roads," said Andrei, a Ukrainian soldier sitting in his truck just outside Artemivsk. "As we were leaving, we were attacked by artillery and grenade launchers. As we moved, we came under attack by tanks and assault groups several times."

He said two of his men had been wounded in the trip.

Andrei spoke of harrowing, almost non-stop fighting for weeks in Debaltseve, where shelling ripped into Ukrainian forces daily.

"Starting at night, they would fire at us just to stop us from sleeping," he said. "They did this all night. Then in the morning they would attack, wave after wave. They did this constantly for three weeks."

A cease-fire for eastern Ukraine was supposed to go into effect Sunday, but Ukrainian military spokesman Anatoliy Stelmakh said rebels had repeatedly shelled a village on the outskirts of the strategic port city of Mariupol in the last day.

The war in eastern Ukraine has killed 5,600 people and forced over a million to flee their homes since fighting began in April, a month after Russia annexed the mostly Russian-speaking Crimean Peninsula. Russia denies arming the rebels or supplying fighters, but Western nations and NATO point to satellite pictures of Russian military equipment in eastern Ukraine.

In Paris, French President Francois Hollande said he and German Chancellor Angela Merkel spoke Thursday with the leaders of Ukraine and Russia about cease-fire violations and their consequences. The Kremlin confirmed the four leaders had spoken by phone and praised the cease-fire deal, saying it has led to "a reduction in the number of civilian casualties."

France and Germany, which oversaw marathon peace talks between the Ukrainian and Russian leaders last week in Minsk, Belarus, both signaled Thursday they're determined to salvage the cease-fire deal and keep the two sides talking despite the rebel capture of Debaltseve.

The German government said the four leaders had agreed "to stick to the Minsk agreements despite the serious breach of the cease-fire in Debaltseve." It said "immediate concrete steps" were necessary to ensure that the cease-fire is fully implemented and heavy weapons are withdrawn.

Paris and Berlin appeared to hope that, after the fall of Debaltseve, the cease-fire in eastern Ukraine will now take hold.

A top French official, speaking on condition of anonymity because he was not authorized to talk about the ongoing negotiations, described the attitude as "pragmatic" and said the alternative to the cease-fire — continued fighting — "was not acceptable to us."

Germany has lowered expectations for the cease-fire.

"The European governments, Germany and France together, will not ease off on doing everything so that Ukraine can go its way and have its territorial integrity — but we want to do it with Russia, not against Russia," German Chancellor Angela Merkel said at a political rally on Wednesday evening.

An analyst said, despite public anger in the capital of Ukraine over the fall of Debaltseve, an overall cease-fire was probably more important than who controls one town.

"(Germany is) more clearly aware than many in Kiev that Ukraine basically needs a cease-fire or a freezing of the conflict more urgently than Moscow," said Gustav Gressel, a visiting fellow at the European Council on Foreign Relations in Berlin. "So Kiev needs to see sooner or later how it gets out of the war."

"From a German point of view, a continuation of the war is probably a greater evil than a not-so-good end to the war," he added.

Balint Szlanko in Artemivsk, Ukraine, Jim Heintz in Kiev, Ukraine, Laura Mills in Moscow, Lori Hinnant in Paris, and Geir Moulson in Berlin contributed reporting.