Bangladesh Prime Minister Sheikh Hasina said it is necessary to verify whether mosques across the country have been constructed after prior approval from the appropriate authorities and with proper designs, so that incidents like Narayanganj mosque blast don't happen again.

She told the parliament that the concerned authorities have been asked to find out the reasons behind the deadly blast in the mosque on Friday night that caused multiple deaths and injuries.

"Experts have visited the place of occurrence and samples are being collected to this end," she said.

Calling the incident "extremely tragic", she said air-conditioners are sometimes being installed in mosques in an unplanned way and some mosques are built without proper plans.

"It's absolutely essential to make sure if the place is suitable for construction of a structure or permission has been taken from appropriate authorities and design has been made properly. Otherwise, such incidents like mosque blast/fire might happen any time," Hasina told the parliament.

"I directed the cabinet secretary and other authorities concerned to find out the reason behind the blast in a mosque of Naraganganj," she told the Jatiya Sangsad while taking part in a discussion on an obituary motion.

"Six air conditioners were installed at such a small place (mosque). Besides, the mosque has been said to be built on a gas pipe line. Usually, no construction on a gas pipe line is allowed. Has RAJUK given permission? None can give such permission having all time risk of happening such an incident. It is being investigated now," she said.

The premier asked the authorities concerned to look into the matter whether air conditioners are being connected at mosques across the country in an unplanned way or the mosques are being built at unauthorized places.

Describing the explosion in a mosque as a matter of sorrow, Hasina said that her government has taken every possible measure to provide better treatment to the burn injured people, adding that she is exchanging messages about the updates of the injured people with Dr Samanta Lal Sen, chief coordinator of Sheikh Hasina National Burn and Plastic Surgery Institute.