Four of the soldiers died when their armoured vehicle hit a landmine close to the frontline town of Avdiivka, while the fifth was killed in a rebel ambush, Ukrainian spokesman Andriy Lysenko said.
The latest casualties come as Ukrainian and separatist representatives gear up to meet for the first time since the two sides inked a shaky peace deal in February that dampened much of the fighting but failed to halt clashes at key hotspots.
Both Kiev and the insurgents accuse each other of continuing to violate the ceasefire deal despite claims from both that they have withdrawn heavy weapons from the frontline in accordance with the agreement.
Kiev spokesman Lysenko said that rebels continued to bombard government positions with 152mm cannons around Mariupol, the largest remaining Ukrainian-controlled city in the conflict zone, and the rebel stronghold of Donetsk.