At least 13 Ukrainian soldiers were killed and 17 injured in a road accident in Ukraine's conflict-torn east, authorities said Tuesday.The accident occurred in Donetsk region late Monday when an army vehicle carrying volunteers collided with a bus during a military operation, Xinhua reported citing the Ukrainian prosecutor general's office.The injured were sent to a nearby hospital for treatment.The interior ministry said the accident could have been caused by bad weather but the exact cause was yet to be determined. The prosecutor general's office is investigating.