(Reuters) - Ukraine's military said on Monday its forces had contained a Russian advance outside the eastern Ukrainian town of Avdiivka captured last month, but Moscow's troops were regrouping in an area further south.

The capture of Avdiivka last month provided Russia with a security cushion for the regional centre of Donetsk 20 km (12 miles) to the east and prompted Kremlin leader Vladimir Putin to pledge that Moscow's forces would make further advances.

Russia's defence ministry last week said its forces had captured new villages outside Avdiivka.

Ukrainian military spokesperson Dmytro Lykhoviy, speaking on national television, acknowledged that Russian forces were in partial control of two more villages -- but their advance had been halted.

"At the same time, we are saying that in this hottest sector of the direct Russian assault, we are managing to stabilise the situation and the enemy's advance has been halted," he said.

Speaking to U.S.-funded Radio Liberty, Lykhoviy said Russian forces were focusing on an area further south, around the village of Novomykhailivka, where they were "transferring reinforcements from the depths of Russia".

The area had sustained 30 assaults on Sunday, compared to 20 near Avdiivka, the radio quoted him as saying.

"But our defence is holding," he said. "The enemy is expending tremendous efforts but making no headway at all."

An account of the fighting by the Russian defence ministry said Moscow's forces had "as a result of coordinated action continued to occupy more advantageous positions" near Avdiivka. It made no mention of the area near Novomykhailivka.

Reuters could not verify accounts from either side.

Russian forces have focused on securing control of eastern Ukraine in the two-year-old war after their initial attempt to advance on Kyiv failed.

The capture of Avdiivka after months of fighting was their biggest gain in nine months, though the front lines have undergone only limited movement in that time. A Ukrainian counteroffensive has made little headway.

Ukraine's Emergency Services reported that two firefighters had been killed near the eastern Ukrainian town of Kramatorsk -- north of Avdiivka -- when they came under Russian shelling while battling a blaze.

(Reporting by Ron Popeski and Oleksandr Kozhukhar; Editing by Sandra Maler)