KIEV, Feb. 23 - Ukraine accused pro-Russian rebels of opening fire with rockets and artillery at villages in a conflict zone on Monday, all but burying a week-old European-brokered ceasefire deal.

The Ukrainian military said it could not pull weapons from the front as required under the tenuous truce, as long as its troops were still under attack, Reuters reported.

Ukraine's currency, nearly in freefall this month, fell a further 10 percent on Monday on fears that the truce could collapse. The central bank said it would tighten currency rules to sustain the hryvnia. The value of Ukrainian debt also fell, with bonds now trading at 40 cents in the dollar.

The reported shooting came closer to killing off the truce, intended to end fighting that has killed more than 5,600 people, which rebels ignored last week to capture the strategic town of Debaltseve in a punishing defeat for Kiev.

Kiev and its Western allies say they fear the rebels, backed by reinforcements of Russian troops, are planning to advance deeper into territory the Kremlin calls "New Russia". Moscow denies aiding the rebels.

Fighting has diminished since Kiev's forces abandoned Debaltseve on Wednesday, and there were hopeful signs for the truce over the weekend, with an overnight exchange of around 200 prisoners late on Saturday and an agreement on Sunday to begin pulling back artillery from the front.

But Kiev said on Monday that two of its soldiers had been killed and 10 wounded in overnight fighting.

"Given that the positions of Ukrainian servicemen continue to be shelled, there cannot yet be any talk of pulling back weapons," spokesman Vladislav Seleznyov said.

Dmytro Chaly, spokesman for the Ukrainian military in the port of Mariupol, a city of 500,000 people which Kiev fears will be the next target, said rebels opened fire in the afternoon with Grad rockets, artillery and tanks on villages nearby.

Anatoly Stelmakh, another military spokesman, said rebel forces had attacked the village of Shyrokyne on the coast road towards Mariupol overnight.

"The fighters have not stopped their attempts to storm our positions in Shyrokyne, in the direction of Mariupol. At midnight armed groups again attempted unsuccessfully to attack our soldiers. The battle lasted half an hour."

Rebel commander Eduard Basurin denied rebel fighters had launched any such attack, and said the situation was calm. "At the moment all is quiet, there is no shelling," he told Reuters.

The head of the Kiev-controlled Donetsk regional police, Vyacheslav Abroskin, said one police officer was killed and two wounded in Mariupol in a shootout when they stopped a militant "reconnaissance group" carrying explosives in a car. One of the rebels was also killed. (rt/ez)