ATHENS, Greece (AP) — The Greek Defense Ministry says three soldiers have been killed and one was seriously wounded in a mortar-tube explosion at an army firing range in central Greece.

The ministry statement, read out in state television, said the incident occurred Tuesday near the city of Volos, about 330 kilometers (205 miles) north of Athens, when an 81 millimeter mortar shell exploded in the barrel, killing two professional soldiers and a third serving his national service.

The ministry said three days of mourning had been declared for the armed forces while senior ministry officials were going to firing range to lead an investigation.