Yerevan, Armenia, Sept. 26: Separatist authorities in Nagorno-Karabakh said Tuesday that at least 20 people were killed and nearly 300 others injured by an explosion at a crowded gas station as thousands of people rushed to cross into Armenia.

More than 13,500 people — about 12% of the region's population — have fled across the border since Azerbaijan's swift military operation to fully reclaim the region after three decades of separatist rule, Armenia's government said Tuesday morning.

The explosion took place as people lined up to fill their cars at a gas station outside the regional capital of Stepanakert late Monday. The separatist government's health department said that 13 bodies have been found and seven people have died of injuries from the blast, the cause of which remains unclear.

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

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. Azerbaijan's blockade of the only road connecting Nagorno-Karabakh to Armenia caused severe shortages of food, medicine and fuel in the region.

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.

Under the armistice that ended the 2020 fighting, Russia deployed a peacekeeping force of about 2,000 to the region. But Armenian officials and regional authorities complained that the peacekeepers were unwilling or unable to end the blockade.-Agencies