YEREVAN, Armenia (AP) — Separatist authorities in Nagorno-Karabakh said Tuesday that at least 20 people were killed and nearly 300 others injured by an explosion at a gas station.

The breakaway region’s health department said that 13 bodies have been found and seven people have died of injuries after the explosion at the gas station outside the regional capital of Stepanakert late Monday.

It said that 290 people have been hospitalized and scores of them remain in grave condition.

The explosion occurred as thousands of Nagorno-Karabakh residents are fleeing the region for Armenia after Azerbaijan’s swift military operation last week to fully reclaim the region after a three-decade separatist rule.