Explosions in a Ukrainian ammunition depot that killed two civilians overnight is being investigated as a terrorist act, the Ukrainian Defence Ministry said on Friday.
On Thursday, a series of blasts took place in a Ukrainian-controlled military complex in Svatove, a town around 100 km (62 miles) from pro-Russian separatists in eastern Luhansk region.
The fire was started by "the release of a flare that fell onto the territory from outside the base," the ministry said in a statement and added that the incident was being investigated as a "terrorist act."
But the statement did not disclose who is suspected of being behind the attack.
Nighttime video footage showed huge smoke clouds billowing from the depot, which contained 3,500 tonnes of ammunition.
In addition to the two casualties, four civilians and four servicemen were wounded, the Ukrainian military in Luhansk said.
Since a new ceasefire agreement was signed, the violence in eastern Ukraine has reached its lowest point in recent weeks. In eastern Ukraine, the conflict has left more than 8,000 dead, since it began in April 2014.
Western diplomats say 12-point peace plan is far from fully achieved. Local elections will be held in the separatist regions in tandem with the rest of the country, but Kiev administration declared that they would not take place due to security concerns.
The pro-Russian separatists founded their own mini-republics and organized their own elections, but Kiev has stated that it would not recognise them.