Thermobaric munitions, also known as fuel air bombs, work by dispersing an explosive substance in vapor form, which uses oxygen in the air as fuel as it explodes, increasing the explosive force. Thermobaric munitions typically produce large powerful blasts.

“Within minutes, a witness said, a helicopter gunship followed and fired cannons, grenades, and rockets into the crowd as people tried to flee,” the group said.

More than 160 people, including children, were killed in the blast and the subsequent attack by helicopter gunships, Human Rights Watch officials said.

Source: Rights group says Myanmar used thermobaric weapon against civilians – UPI.com