Petr David Josek, Associated Press
Ukrainian government soldiers rest by armored vehicle on the road between the towns of Dabeltseve and Artemivsk, Ukraine, Sunday, Feb. 15, 2015. International attention will be focused in the coming days on the strategic railway hub of Debaltseve, where Ukrainian government forces have for weeks been fending off severe onslaughts from pro-Russian separatists. A cease-fire was declared in eastern Ukraine, kindling slender hopes of a reprieve from a conflict that has claimed more than 5,300 lives.

ARTEMIVSK, Ukraine — The Ukrainian government and Russia-backed rebels accused each other Monday of violating a cease-fire in eastern Ukraine, a day before the parties are due to start withdrawing heavy weaponry under a recently brokered deal.

The cease-fire, which went into effect on Sunday, had raised cautious hopes for an end to the 10-month-old conflict, which has already claimed more than 5,300 lives.

Separatist military spokesman Eduard Basurin said in a televised news conference on Monday that the government launched an artillery strike overnight on Horlivka, a town under rebel control.

Ukraine, however, blamed the attack on the rebels. The government-appointed police chief of the Donetsk region, Vyacheslav Abroskin, said the separatists shelled the town in order to derail the truce.

Both the separatists and the Ukrainian government reiterated their commitment to the cease-fire that was brokered last week in 16-hour talks involving the presidents of Russia, Ukraine, Germany and France. In line with the truce, both parties should begin withdrawing heavy weaponry from their positions early Tuesday.

Continued fighting over the railway hub of Debaltseve, where Ukrainian forces have been fending off onslaughts from the rebels, is threatening to upend the delicate settlement. Rebels argue they should be granted immediate control over the town, which links the main separatist-held cities of Donetsk and Luhansk, as it is entirely surrounded by their forces. Separatist officials have said any force adopted against Ukrainian troops in Debaltseve would accordingly not violate the Minsk agreement.

Fighting around Debaltseve continued early morning on Monday as the separatists launched an air strike on the town, Abroskin said.

In New York, UN Secretary General Ban Ki-moon expressed concern in a statement late on Sunday over continued hostilities around Debaltseve and reiterated his call "for all parties to abide by the cease-fire without exception."