KIEV, Ukraine 

Five Ukrainian soldiers were killed and 25 others were wounded during the last 24 hours in eastern Ukraine, a Ukrainian official said Monday.

Ukraine’s Anti-Terrorism Operation spokesman Andriy Lysenko accused pro-Russian separatists of violating a cease-fire that began Feb. 15 at least 112 times.  

Lysenko said the situation remained tense in Debaltseve, a region controlled by the government, and added that the fighting between Ukrainian soldiers and pro-Russian separatists was ongoing.

The rebels allegedly fought with Ukrainian troops last night in the Shirokino borough, near Mariupol, as well.

The spokesman said the Ukrainian government did not plan to withdraw heavy weapons from the front lines. "As long as the first article of the Minsk Accord, the cease-fire, is not implemented, we cannot implement the second article," he said.

Michael Bociurkiw, chairman of Organization for Security and Co-operation in Europe’s special monitoring mission, said despite "some violations" in Debaltseve, the cease-fire was being respected.

But in Washington, State Department spokeswoman Jen Psaki said the U.S. "is gravely concerned by the deteriorating situation in and around Debaltseve." 

Fighting between government forces and pro-Russian separatists broke out in Ukraine's Donbass region last April.  In September and December 2014, the two sides managed to reach two cease-fire agreements, which lasted until January 2015.

When the cease-fire regime collapsed Jan. 12, fighting broke out throughout the region, with separatist forces going on the offensive at several locations.

On Feb. 7, French President Francois Hollande joined German Chancellor Angela Merkel for a surprise visit to Moscow to discuss a peace proposal.

Hollande, Merkel, Russian President Vladimir Putin and Ukrainian President Petro Poroshenko signed a cease-fire agreement Feb.12, according to which a cease-fire was to enter into effect at midnight Feb. 15, and heavy weapons were to be pulled back by both sides.

Psaki said the cease-fire and the planned withdrawal of heavy weapons were being threatened by the rebels, adding that the U.S. is monitoring reports of a "new column of Russian military equipment moving toward Debaltseve."