The blast occurred Friday night as people were finishing their prayers at Baitus Salat Jame Mosque at Narayanganj, local police chief Zayedul Alam said, AP reported.
By Saturday morning, a young boy and 10 others succumbed to their injuries as doctors at a burn unit of a state-run hospital were treating at least 37 people with up to 90% of burns on their bodies, said Samanta Lal Sen, a coordinator of the unit.
Most were in critical condition, Sen said.
TV stations reported that because of the impact of the blast, at least six air conditioners also exploded inside the mosque. Firefighters were investigation the cause.