KIEV, Feb. 19 - 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, Reuters reported.

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 demoralized 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.

Wednesday's withdrawal was a humiliating defeat for Ukrainian President Petro Poroshenko, who faces an economic crisis as well as the war.

The Ukrainian Defense Ministry said 13 servicemen were killed and 157 wounded during the withdrawal and a further 82 were still missing. Ninety-three were taken prisoner.

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. (rt/ez)