UN Secretary-General Ban Ki-moon has joined other leaders voicing concern over an increase in fighting in the conflict between governing forces and pro-Russian separatists in eastern Ukraine.
Ban said in a statement on January 18 that he was "alarmed by the severe escalation of fighting."
The UN chief called for "an immediate and full cessation of hostilities."
He said the fighting threatens to completely scuttle a 12-point peace plan signed by representatives of Ukraine, Russia, and the rebels in Minsk on September 5.
A Ukrainian military spokesman said on January 18 that four soldiers had been killed in the previous 24 hours, three of them in fierce fighting in which Kyiv says its forces took almost all the territory of Donetsk airport lost to separatists in recent weeks.
Some reports said at least 14 people were killed over the weekend.
More than 4,700 people have been killed in the conflict since April.