More than 13,500 people — about 12 per cent of the region's population — have fled across the border since Azerbaijan defeated separatists who have governed the breakaway region for about 30 years in a swift military operation last week, Armenia's government said.
Residents of Nagorno-Karabakh scrambled to flee as soon as Azerbaijan lifted a 10-month blockade on the region's only road to Armenia.
That blockade had caused severe shortages of food, medicine and fuel. While Azerbaijan has pledged to respect the rights of Armenians, many residents feared reprisals.
The explosion took place as people lined up to fill their cars at a petrol station outside Stepanakert, the region's capital, late on Monday.
The separatist government's health department said that 13 bodies have been found and seven people have died of injuries from the blast; another 290 people have been hospitalised and scores of them remain in grave condition.
The cause of the blast remains unclear, but Nagorno-Karabakh presidential aide David Babayan said initial information suggested that sabotage was unlikely.
Armenia's health ministry said a helicopter brought some blast victims to Armenia on Tuesday morning, and more flights were expected. The Russian peacekeeping force in Nagorno-Karabakh also reportedly was bringing in victims to Armenia by helicopter.
Azerbaijani presidential aide Hikmet Hajiyev said on X, formerly Twitter, that hospitals in Azerbaijan were ready to treat victims, but did not say if any had been taken there. Azerbaijan has sent in burn treatment medicine and other humanitarian aid, he said.
Azerbaijan also said on Tuesday that 30 tonnes of petrol and 34 tonnes of diesel fuel were being sent into the region.
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.
Petrol has been in short supply in Stepanakert for months, and the explosion further adds to anxiety about whether residents will be able to drive the 35km to the border.
Cars bearing large loads on their roofs crowded the streets of Stepanakert, and residents stood or lay along sidewalks next to heaps of luggage.
Nagorno-Karabakh authorities asked residents to hold off on leaving in order to keep the road clear for emergency services and said buses would be provided for those who want to leave.
Nagorno-Karabakh was an autonomous region within Azerbaijan under the Soviet Union, but separatist sentiment grew in the USSR's dying years and then flared into war.
Nagorno-Karabakh came under the control of ethnic Armenian forces, backed by the Armenian military, in separatist fighting that ended in 1994.
During a war in 2020, Azerbaijan took parts of Nagorno-Karabakh along with surrounding territory that it lost of control of during the earlier conflict.
Under the armistice that ended the 2020 fighting, Russia deployed a peacekeeping force of about 2000 to the region.
