Several Ukrainian government soldiers have been ambushed and taken prisoners in Debaltseve, the defense ministry said Tuesday, but denied rebel claims that they have seized control of the key transportation hub.

The ministry said street fighting continued in Debaltseve, which has been the epicenter of fighting in the past two weeks. It did not say how many soldiers had been seized in the ambush.

The Ukrainian presidential office earlier Tuesday called on the European Union and NATO to condemn the Russia-backed rebels for violating the cease-fire brokered by European leaders last week.

Russian news agencies quoted Valery Chaly, chief of the Ukrainian presidential administration, as saying that Kiev wants the EU and NATO to “resolutely condemn” the separatists for violating the deals.

The war in eastern Ukraine has already killed more than 5,600 people and displaced more than a million, the United Nations said on Monday. It has also left the country’s industrial heartland in ruins.

The government troops and rebels faced a deadline Tuesday to start pulling back heavy weapons from the front line.

Rebel commander Vladimir Kononov said on Russian television that most of Debaltseve was under their control and urged the Ukrainian troops to surrender.

“Their only choice is to leave behind weaponry, lay down arms, and surrender,” he said.

The announcement by the rebels came after fierce fighting that appeared to be focused on Debaltseve. Both sides in the conflict claim the town is on their side of the cease-fire line. The issue was not resolved under the cease-fire agreement negotiated last week by the leaders of Ukraine, Russia, Germany, and France.

Also Tuesday, a deadline passed under the agreement for both sides to begin pulling back weaponry from the front line.

The rebels said they were about to begin withdrawing their big guns on some sections of the frontline. A rebel military official, Eduard Basurin, announced in a televised briefing that they “will take the initiative” and begin to pull back heavy weaponry from the frontline. He did not provide a timeline for this.

The Ukrainian government, however, insisted on a comprehensive cease-fire before pulling back its weaponry.

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.

Ukrainian military spokesman Andriy Lysenko told reporters Tuesday that the separatists continued to attack government positions overnight around 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, which was brokered by European leaders last week and went into effect early Sunday, specifies the pullout begins 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.

Fighting has stopped or subsided in some parts of war-torn eastern Ukraine, however. Basurin said Tuesday they separatists had not seen any violations of the cease-fire in the area around the rebel stronghold of Donetsk since 8 p.m. Monday.

Rupert Colville, spokesman for the U.N. High Commissioner for Human Rights, told a briefing in Geneva on Tuesday that the UN is “alarmed” by reports of continued shelling in the areas and have not yet been able to get reliable information on the casualties there and the wellbeing of civilians.

“It is unclear how many civilians are still there,” he said. “We are particularly concerned about the civilians trapped in the area – we believe there may be a few thousand hiding in cellars, struggling to get food, water and other basic necessities.”

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.

Reporting by The Associated Press

Former U.S. Ambassador Kenneth Yalowitz discusses Ukraine ceasefire

CCTV America interviewed Kenneth Yalowitz on the fighting in eastern Ukraine. He’s a former U.S. Ambassador to Belarus and Georgia and worked in Moscow during his time with the Foreign Service.