Kiev and pro-Russian separatists Sunday accused each other of firing on their positions around the ruins of Donetsk airport, a flashpoint in eastern Ukraine.
The Ukrainian military also said two soldiers were killed in the region on Saturday when they stepped on landmines.
"The Oktyabrsky district around Donetsk has been the target of mortar fire from Pisky and Avdiivka", areas controlled by the Ukrainian army, a rebel military spokesman, Eduard Basurin, told AFP.
Ukrainian military spokesman Olexandr Zavtonov said "the enemy fired grenade launchers at our positions in Pisky," where two Ukrainian soldiers were killed last week in rebel attacks.
Donetsk airport was for several months the scene of fierce fighting between the Ukraine army and pro-Moscow insurgents before falling into separatist hands in January, and remains a flarepoint.
The latest attacks highlight the fragile nature of the latest ceasefire, in place since September 1, in a conflict which has cost more than 8,000 lives in the past 18 months.
The lull in fighting has raised hopes of an end to one of Europe's deadliest conflicts since the Balkan wars of the 1990s, but the process has been slow and periodic exchanges of deadly mortar fire still flare up.
The sporadic fighting and seemingly irreconcilable differences over the pro-Russian regions' future status within a unified Ukraine means that a peace process that was meant to be finished by the end of the year will drag on into 2016.

AFP