The blast occurred on Friday night just as mosque visitors ended their prayers to leave the building.
One of the victims was a child.
A number of people are now being cared for in hospitals with severe burns as a result of the explosion.
The death toll is feared to rise as the condition of many of the injured is critical.
Authorities have launched an investigation into the incident, a gas leak from management is believed to be what caused the explosion.
- We suspect that gas leaked from the pipeline, and that gas was collected inside the mosque when the building's windows were closed.
When the air conditioning was turned on, sparks appeared which caused the gas to explode, says Abdullah al-Arifin at Dhaka's fire protection authority.