| ARTEMIVSK/VUHLEHIRSK, Ukraine
ARTEMIVSK/VUHLEHIRSK, Ukraine Fighting raged in eastern Ukraine on Thursday despite European efforts to resurrect a stillborn ceasefire, a day after pro-Russian separatists spurned the truce by forcing thousands of government troops out of a strategic town.
Western nations are refusing to give up on a peace deal brokered by France and Germany last week even though the rebels disavowed it to seize the important railway hub of Debaltseve.
Shelling continued near that town on Thursday, and local officials in government-held territory said rebels had also fired mortar bombs at another town further south. Kiev fears they are massing for an assault near the major port of Mariupol.
Thousands of weary and demoralised soldiers withdrew from Debaltseve on Wednesday in one of the worst defeats suffered by Kiev during 10 months of fighting in which more than 5,000 people have been killed.
European and U.S. officials have expressed hope that the ceasefire will hold now that the rebels, fighting for territory Russian President Vladimir Putin has called "New Russia", have achieved their immediate goal of taking Debaltseve.
But Reuters correspondents outside the rebel-held town of Vuhlehirsk said artillery shells were still falling on nearby Debaltseve, though with less intensity than earlier this week.
Reporters in the main rebel stronghold of Donestsk said there was also shelling in the area.
The Kiev government's biggest fear is of a rebel assault on Mariupol, a port of 500,000 people and by far the biggest government-held city in the two rebellious eastern provinces.
"Right now there are mortar attacks on Shyrokine," a military spokesman said, referring to a village about 30 km (20 miles) east of Mariupol, along the coast of the Sea of Azov.
"There is no attempt to seize our positions up to now. The rebels are bringing up reserves," the spokesman said.
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Wednesday's withdrawal was a humiliating defeat for Ukrainian President Petro Poroshenko, who faces an economic crisis as well as the war. Images of captured Ukrainian soldiers were beamed across Russia.
The Ukrainian Defence Ministry said 13 servicemen were killed and 157 wounded during the withdrawal and a further 82 were still missing. Ninety-three were taken prisoner.
"There are no words to describe it. Along the entire way we were blanketed with shots, wherever there were trees they fired at us from machine guns and grenade launchers. They used everything," Vadim, a soldier from Ukraine's 30th brigade, told Reuters in Artemivsk, a government-held town north of Debaltseve where the soldiers assembled after they withdrew.
Some blamed commanders for leaving them trapped in the besieged town after it became impossible to resupply it.
"It felt like we'd been abandoned or betrayed," said a soldier from Ukraine's 55th brigade.
Ukrainian military spokesman Andriy Lysenko said more than half a tonne of "deadly metal, in the shape of rocket shells, mortar, anti-tank rockets and other hardware, came down on the head of every soldier on average every day" from the start of the ceasefire on Sunday until the withdrawal.
The rebels have maintained that the ceasefire did not apply to Debaltseve, suggesting they may begin to observe it now that they have captured the town. They have announced that they are pulling back heavy guns as required under the truce.
The leaders of Germany, France, Ukraine and Russia agreed in a telephone call to make a new attempt to enforce the ceasefire and ensure other terms of the peace deal are implemented.
But deep mistrust means Western leaders including German Chancellor Angela Merkel, who led the drive that resulted in the peace deal signed in the Belarussian capital Minsk last week, see only a glimmer of hope of ending the fighting.
The White House said it was "deeply troubled" by reports of fighting and NATO's top military commander, U.S. Air Force General Philip Breedlove, said he did not think the truce had ever even begun.
"It is a ceasefire in name only," Breedlove said during a visit to Kosovo.
Western countries say Russia is behind the rebel advance, having deployed thousands of troops with advanced weaponry into eastern Ukraine to fight on the separatists' behalf, though Moscow denies this.
British Defence Secretary Michael Fallon said Putin posed a "real and present danger" to Estonia, Latvia and Lithuania and NATO was getting ready to repel any aggression.
Moscow said the comments went beyond "diplomatic ethics".
Valdis Dombrovskis, vice president of the European Commission, said "Russia is looking to redraw Europe's 21st century borders by force".
Moscow dismissed a call by Ukraine for United Nations peacekeepers to come to east Ukraine. Russia said the Minsk agreements should be the basis for peace, not peacekeepers. As a permanent member of the Security Council, it could block any move to send peacekeepers.
Russia has in the past proposed sending its own peacekeepers but the OSCE security watchdog, which has observers in east Ukraine, ruled out a Russian role in any force, describing Moscow as an "aggressor".
(Additional reporting by Richard Balmforth and Pavel Polityuk in Kiev, Fatos Bytyci in Pristina; Writing by Timothy Heritage and Peter Graff; Editing by Giles Elgood)