The Ukrainian president's office says at least three troops have been killed and 15 injured in fighting in eastern Ukraine in the past 24 hours.

Government troops and Russia-backed rebels last month agreed to cease fire by Sept. 1, the first day of school in the country, but the new truce seems to be failing.

Olexander Motuzyanyk, presidential spokesman for the operation in the east, said on Tuesday that two people were killed in fighting to the north of the conflict zone and another by artillery fire to the south. One more person was reported missing and 15 injured.

Russian President Vladimir Putin discussed the situation in eastern Ukraine earlier this month with German Chancellor Angela Merkel, who has been a key mediator between Russia and Ukraine.