Pro-russian rebels killed four Ukrainian soldiers and wounded 14 in the past 24 hours, according to the Ukrainian military.
“Renewed rebel shelling of government positions near the separatist-held city of Donetsk and mortar fire in villages near the strategic Kiev-controlled port city of Mariupol” were reported by Ukrainian military spokesman Oleksander Motuzyanyk on Thursday.
"In this area the enemy does not engage in direct fighting with the Ukrainian army, but fires chaotically from howitzers and GRAD multiple rocket launchers," Motuzyanyk said.
The Russian-backed separatist officials accused Ukrainian troops in turn of shelling rebel territory, including residential areas.
France and Germany, who helped broker the six-month-old truce between Ukrainian forces and pro-Russian separatists, scheduled new talks with Ukranian President Petro Poroshenko to debate how to preserve the peace in the face of a remarkable increase in military and civilian casualties in the past two weeks.
Any attempt by the rebels to take more of Ukraine's territory would be unacceptable, NATO warned Russia on Wednesday, which the West accuses of supporting the separatists with equipment and fighters.
Poroshenko will meet German Chancellor Angela Merkel and French President Francois Hollande in Berlin on Monday to discuss the latest escalation in the conflict, during which over 6,500 people been killed since fighting began in April 2014.