The Ukrainian military says three soldiers have been killed and eight wounded in fresh fighting between government forces and Russia-backed separatists in the east of the country.

Military spokesman Andriy Lysenko said on May 30 that fighting had intensified compared to a month ago and accused separatists of "actively using heavy weapons," including a Grad rocket launcher.

Lysenko said the latest clashes were reported around the separatist-controlled city of Donetsk and the government-controlled city of Mariupol on the coast of the Sea of Azov.

Ukrainian forces have suffered significant losses in eastern Ukraine in recent days. On May 24, Kyiv said seven soldiers were killed in fighting with separatists. On May 28, five more soldiers were reported killed.

Amid the flare-up in violence, Ukrainian President Petro Poroshenko has called for greater foreign assistance and has appointed former NATO Secretary-General Anders Fogh Rasmussen as his adviser.

Last month, Ukrainian Defense Minister Stepan Poltorak said it could take years to end the conflict, which has claimed more than 9,300 lives since it erupted in April 2014.

Based on reporting by AFP and Interfax