The deadly blast occurred as thousands of ethnic Armenians fled the breakaway enclave after their fighters were defeated by Azerbaijan in a lightning military operation.
Many of those leaving have said they fear persecution and ethnic cleansing at the hands of Azerbaijan.
The Armenians of Karabakh began fleeing this week after their forces were routed in a lightning operation by Azerbaijan's military.
Thousands of ethnic Armenians fled the breakaway region of Nagorno-Karabakh by Monday after their fighters were defeated by Azerbaijan.
Azerbaijan says it will guarantee their rights and integrate the region but the leadership of the Armenians in Karabakh stated that they would leave.
The Armenians of Karabakh, which is internationally recognized as part of Azerbaijan, were forced to declare a ceasefire earlier this week.
Azerbaijani President Ilham Aliyev said the country had had regained full sovereignty over its territory and now wished to integrate Karabakh's population and turn the region into "paradise."