At least two people have been killed in fighting in eastern Ukraine, officials said as Russia claimed it carried out deadly missile strikes on barracks used by Ukrainian troops in the war.
Donetsk governor Pavlo Kyrylenko said one person died in strikes on Bakhmut and eight others in the region were hurt.
He also reported rocket attacks on Kramatorsk and Konstantynivka.
In the Kharkiv region, the town of Merefa was hit during the night, killing one person, while two other settlements in the region were shelled, governor Oleh Syniehubov said.
The Russian military said missiles launched at Kramatorsk hit barracks used by Ukrainian troops, killing 600 people.
The Ukrainian military says this is untrue. Serhiy Cherevaty, a spokesman for the Ukrainian army, told the BBC: "This is another piece of Russian propaganda."
It comes almost a week after Ukraine forces fired rockets at a facility in the eastern Donetsk region where Russian soldiers were stationed, killing dozens of them in one of the deadliest attacks on the Kremlin's forces since the war began over 10 months ago.
Russian defence ministry spokesman Igor Konashenkov said the missile strikes were retaliation for Ukraine's attack in Makiivka, in which at least 89 Russian soldiers died.
"Over the past day, Russian intelligence means detected and reliably confirmed through various independent channels some temporary bases of Ukrainian servicemen in Kramatorsk," he said.
"As a result of a massive rocket strike on these temporary bases of Ukrainian units, more than 600 Ukrainian servicemen were killed."
Seven missile strikes were launched on Kramatorsk overnight, damaging an "educational facility and an industrial facility", the Ukrainian news agency Ukrinform said.
It quoted Mr Kyrylenko as saying: "In Kramatorsk, the buildings of an educational institution, an industrial facility and a garage co-operative were damaged."
Ukrinform said "according to preliminary information, nobody was injured during the shelling".
The latest developments come after Russian forces ended a partially observed, unilateral ceasefire timed to coincide with Orthodox Christmas celebrations on Saturday.