Unrest in eastern Ukraine has torn the region apart since April, when Kiev began operations against armed separatists.
At least 15 Ukrainian soldiers were killed and 89 wounded in the past 24 hours in clashes between pro-Russian separatists and the Ukrainian army in the country's eastern regions, said spokesman for Ukraine's National Security Council.
Unrest in eastern Ukraine has torn the region apart since April, when Kiev began operations against armed separatists.
Russia faced a first wave of sanctions after annexing Crimea in March. Another wave followed after the downing of a Malaysian airliner that killed all 298 passengers and crew members onboard.
After Russia annexed Crimea in March following a referendum in the peninsula, pro-Russian separatists, hoping for a repeat scenario in eastern Ukraine, expressed their intention to break away from the central Kiev government.
At least 500 people have been killed since the Ukrainian army launched an "anti-terror" operation against pro-Russian separatists in April.