The death toll from an explosion-triggered fire at a mosque outside the Bangladeshi capital Dhaka has risen to 11, police and physicians said on Saturday.

The explosion occurred on Friday night when Muslim worshippers were about to end their evening prayers at Baitus Salat Jame Masjid in Narayanganj district, nearly 25 kilometres south of Dhaka, Police officer Zayedul Alam said.

He added that 37 out of 40 victims with severe wounds were rushed to Dhaka’s state-run specialised burn and plastic surgery institute.

Overnight, 10 people died at the hospital, physician Partha Sankar Paul told reporters.

A seven-year-old boy, who had burns on nearly 95 per cent of his body died hours after he was admitted at the hospital, according to Samanta Lal Sen, head of the institute.

He earlier told reporters that most victims were in a critical condition.

Television footage showed relatives of the deceased wailing outside the hospital.

Members of the Fire Service and Civil Defence Department, who extinguished the fire and rescued the victims, said a gas leak might have caused the explosion.

“Primarily, we are suspecting that gas accumulated from a line beneath the mosque might have caused the explosion,” firefighting official Abdullah Al Arefin said.

Six air-conditioners inside the mosque also exploded, he said, adding that an investigation had been launched to determine the reason behind the accident.