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 as people seeking to flee to Armenia lined up for fuel.

The breakaway region’s health department said that 13 bodies have been found and seven people have died of injuries suffered in 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 residents were lining up to get fuel for their cars in order to leave the region. Thousands of Nagorno-Karabakh residents are fleeing to Armenia after Azerbaijan’s swift military operation to fully reclaim the region after a three-decade separatist rule.

The Azerbaijani military routed Armenian forces in a 24-hour blitz last week, forcing the separatist authorities to agree to lay down weapons and start talks on Nagorno-Karabakh’s “reintegration” into Azerbaijan. While Azerbaijan has pledged to respect the rights of ethnic Armenians in the region and restore supplies after a 10-month blockade, many local residents feared reprisals and decided to leave for Armenia.

The Armenian government said that more than 6,500 Nagorno-Karabakh residents had fled to Armenia as of Monday evening. Moscow said that Russian peacekeepers in Nagorno-Karabakh were assisting the evacuation. Some 700 people remained in the peacekeepers’ camp there by Monday night.

Nagorno-Karabakh came under the control of ethnic Armenian forces, backed by the Armenian military, in separatist fighting that ended in 1994. During the war in 2020, Azerbaijan took back parts of Nagorno-Karabakh along with surrounding territory that Armenian forces had claimed during the earlier conflict.