The Ukrainian government has accused Russia-backed rebels in eastern Ukraine of violating the shaky truce with large-caliber weapons.

The military conflict between government forces and separatist rebels in Ukraine's industrial heartland has left more than 9,000 people dead since April 2014. Fighting subsided last year after a series of cease-fire agreement but seems to have flared up this week.

The press office of the Ukrainian government's operations in the east said in a statement on Friday that the rebels had opened fire on its forces 81 times over a 24-hour period, using grenade launchers and large-caliber weapons that should have long been withdrawn.

International observers at the Organization for Security and Cooperation in Europe earlier this week spoke of a "massive increase" in violence in the east.