LUHANSKE, Ukraine — Under a near-constant barrage of artillery fire, Ukrainian forces and separatist rebels fought fierce street battles Tuesday for control of the strategic railway hub of Debaltseve, a battle impeding implementation of a peace plan.

Ukraine denied rebel claims to have taken control of the town but acknowledged the separatists had seized parts of it.

The battle came despite a weekend cease-fire that obliged both sides to start moving back their big guns on Tuesday.

A key railroad junction between the separatist east’s two main cities of Donetsk and Luhansk, Debaltseve has been the focus of fighting over the past two weeks and capturing it would be a prize for the Russia-backed rebels.

The defense ministry said street battles continued there Tuesday and government soldiers had been ambushed and taken prisoner, but gave no details on how many were seized. Rebel spokesman Eduard Basurin said hundreds of Ukrainian soldiers had surrendered in Debaltseve.

Associated Press journalists were turned back by Ukrainian forces at Luhanske, a village about 10 miles north of Debaltseve and were unable to assess the status of the fight.

The leader of the self-proclaimed Donetsk People’s Republic, one of two separatist entities, was wounded in the leg and hospitalized in the neighboring Luhansk region, Russia’s RIA-Novosti news agency quoted a Luhansk rebel official as saying. Zakharchenko’s life was not in danger, the report said.

The Ukrainian presidential office called on the European Union and NATO to condemn the Russia-backed rebels for violating the cease-fire brokered by the leaders of Ukraine, Russia, Germany and France last week.

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

On Tuesday, a deadline passed for both sides to begin pulling back heavy weapons from the front line.

Rebel commander Vladimir Kononov said on Russian television that most of Debaltseve was under separatist 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, and the issue was not resolved under the cease-fire deal.