A unilateral ceasefire called by Russia appears to have had little effect on fighting on the ground, with officials accusing each other of opening fire on several areas.
A Ukrainian rescue worker was killed in a Russian strike, while Russian state TV said the city of Donetsk was hit.
Russia ordered a 36-hour unilateral ceasefire to coincide with the Orthodox Christmas.
Ukraine rejected it, saying Moscow might use it to reinforce troops.
Russia’s defence ministry insisted it was observing the truce along the entire “line of contact”, starting at 12:00
Moscow time (09:00 GMT) on Friday. It blamed Kyiv for continuing to shell Russian positions and settlements in occupied Ukraine.
Air alerts were reported across Ukraine shortly after the purported truce began, and then the governor of Kherson region said a strike on a fire station left rescuer dead and four other people wounded in the main city, liberated in November by Ukrainian forces.
The eastern city of Kramatorsk also came under attack and more than a dozen buildings were damaged, Ukrainian officials said.
Luhansk regional leader, Serhiy Haidai, warned that Russia’s Christmas truce was “a lie and a trap”, advising residents not to attend Orthodox Church services or gather in crowded places as the Russians could plan “terrorist attacks”.
Kyiv Mayor, Vitaliy Klitschko, warned that overnight temperatures in the capital would drop to -11C and called for electricity to be carefully used.
Ukraine’s President, Volodymyr Zelensky, said the truce was an attempt to stop his country’s military advances in the east of the country, and bring in more men and equipment. Artillery fire could be heard on both sides of the front line in the eastern city of Bakhmut, where Russian forces have concentrated much of their firepower in an attempt to push west towards Kramatorsk. -BBC