Ukraine's military said 14 people, including at least 10 soldiers, were killed in an ambush by pro-Russian separatists near the town of Shakhtarsk, in eastern Donetsk region, early on August 1.
Military spokesman Oleksiy Dmytrashkivsky said the death of 10 soldiers has been confirmed but that four other bodies had not been identified and could be either soldiers, or separatists.
Ukraine's military has recently forced the separatists out of some areas they held in the east after days of intense fighting.
Shakhtarsk is in the area where a Malaysian airliner came down on July 17, allegedly shot down by the separatists.
A team of Dutch and Australian police and crash experts visited the crash site for the first time on July 31, having been unable to reach the site for days because of the heavy fighting.