Russia's Defense Ministry claimed Sunday it had killed more than 600 Ukrainian servicemen in a massive rocket strike on two buildings in eastern Ukraine temporarily housing Ukrainian forces.

Moscow said the "retaliatory strike" in the eastern Ukrainian city of Kramatorsk was to avenge the deaths of 89 Russian troops killed in Makiivka.

"More than 600 Ukrainian servicemen were killed" as a result of a strike on Kyiv troops stationed in two buildings in Kramatorsk used as barracks, the Russian defense ministry claimed in a statement, calling the attacks a "retaliatory strike."

AFP could not immediately verify the report but Reuters reported that a Russian rocket caused damage but did not destroy buildings and there were no obvious signs of casualties.

Reuters reporters visited the two college dormitories Russia's defense ministry said had been temporarily housing Ukrainian servicemen close to the front line of the war at the time of the overnight strike.

Neither appeared to have been directly hit by missiles or seriously damaged. There were no obvious signs that soldiers had been living there and no sign of bodies or traces of blood.

Some of the windows were broken at Hostel No. 47, which stood by a courtyard that had a big crater in it, reported Reuters.

The other building named by Russia's defense ministry, Hostel No. 28, was entirely intact. A crater lay about 50 meters away closer to some garages.

Authorities in Kyiv did not immediately comment on the strike or on Russia's claim of hundreds of casualties. Kramatorsk's mayor earlier said there had been no casualties.

Earlier Sunday, Pavlo Kyrylenko, the head of the Donetsk regional administration, said Russians launched seven rocket attacks on Kramatorsk.

He said that "an educational institution, an industrial facility and a garage cooperative" had been damaged and that there were no casualties.

In a New Year's attack, Ukraine struck a building in the occupied eastern Ukrainian town of Makiivka being used as a barracks.

Russia conceded 89 troops had died, in what was the worst single reported loss from a Ukrainian strike.

Russian President Vladimir Putin had ordered a 36-hour cease-fire to allow Orthodox Christians to mark Christmas which is celebrated on Jan. 7 in Russia and Ukraine.

The unilateral ceasefire ended at 11 p.m. in Kyiv (9 p.m. GMT) on Saturday.