LUHANSKE, Ukraine — Russia-backed separatists say they have gained control of a key rail hub in eastern Ukraine.

The Donetsk News Agency, a rebel mouthpiece, quoted the rebels' so-called defense ministry as saying Tuesday that their forces have pushed government troops out of Debaltseve and are now controlling a large part of it.

Fierce fighting on Tuesday, two days after a cease-fire was announced for eastern Ukraine, appeared to be focused on Debaltseve, which both sides claim is on their side of the cease-fire line.

Government troops and the separatists were expected to begin withdrawing heavy weaponry from the front line on Tuesday but Associated Press reporters saw no sign of that on the ground.

Ukrainian military spokesman Andriy Lysenko told reporters Tuesday that the separatists continued to attack government positions overnight around the town of Debaltseve and that the pullout hinged on the cease-fire being fully observed. He said at least five troops were killed and nine injured in the past 24 hours in the war zone.

The cease-fire deal, brokered by European leaders last week, specifies the pullout begin on the second day after the parties stop fighting. This condition has not been met, Lysenko said.

"As soon as the fire ceases ... we will be ready to begin the withdrawal," he said.

The war in eastern Ukraine has already killed more than 5,600 people and displaced more than a million, according to U.N. figures issued Monday. It has also left the country's industrial heartland in ruins.

Fighting has stopped or subsided in some parts of war-torn eastern Ukraine, however. Rebel mouthpiece the Donetsk News Agency quoted rebel officials saying Tuesday they had not seen any violations of the cease-fire in their area since 8 p.m. Monday.

Associated Press reporters saw artillery rounds fired Tuesday from Ukrainian government positions at rebel positions around Debaltseve. Sustained shelling was heard in the area all morning, some coming from Grad rocket launchers.

Debaltseve is a government-held town surrounded by rebel forces, and both sides claim it should be on their side of the cease-fire line. The issue was not resolved under a cease-fire agreement negotiated last week by the leaders of Ukraine, Russia, Germany and France.

Elsewhere, at least one rebel leader claimed that his troops had begun to withdraw their heavy weapons.

"I was at the front line last night, and our tanks, our artillery were pulling back," Igor Plotnitsky, the leader of the self-proclaimed Luhansk People's Republic, northeast of Debaltseve, was quoted as saying by the Russian news agency Tass.

He added that he "expects the same from Ukraine."

Due to security issues, his claims could not be immediately verified. Lysenko said the Ukrainian troops "have not noticed any such actions" on the ground.

The separatists were expected to discuss the withdrawal of the weaponry later Tuesday with representatives of Ukraine, Russia and the group charged with monitoring the cease-fire, the Organization for Security and Cooperation in Europe.

In a phone call late on Monday German Chancellor Angela Merkel and Ukrainian President Petro Poroshenko appealed to Russian President Vladimir Putin to use his influence on the separatists to ensure that they stop the fighting.

Merkel's office reported that the three leaders agreed on "concrete steps to enable an observation" of the situation in Debaltseve by the OSCE. It did not elaborate on what these steps would be.

OSCE representatives could not get to Debaltseve on Monday because of the heavy fighting there.