Moulvibazar: Militants overnight staged a suicide blast blowing up their entire family of presumably eight members in their den on the face of a security assault on the outskirts of Moulvibazar, police said on Thursday.

"The suicide blast blew up all who were inside the hideout . . . we assume seven to eight including minor children were there when the militants exploded a powerful device last night as we laid the siege to the den," police's counter terrorism unit chief Monirul Islam told a media briefing at Nasirpur.

He added that the blast was so severe that it split into pieces the dead making it difficult to ascertain exactly how many people were inside.

"The forensic examinations could confirm the casualty figure but we assume they are seven or eight in number," Islam added. He said the militants responded blasting explosives to police calls for their surrender and eventually they exploded a powerful device last night which was apparently blew them all.

He said police entered the house after a drone was flown into the den to send out a grab pictures of the situation inside earlier today and found out that the entire family committed suicide, finding no way to flee the siege". 

A neighbour who live in a house adjacent to the den, however, earlier, told newsmen at the scene that two couples having five children aged between one and seven years while they used to live in the house as tenants.

"One of the couple was senior while the other couple was their daughter and son-in-law," said the neighbor, a rickshaw puller who preferred to be unnamed while talking to the journalists at the scene.

He added that the two couples always led a secretive life and even barred the children from interacting with neighbours.

But he said police's Special Weapons and Tactics (SWAT), backed by other police units including elite anti-crime Rapid Action Battalion (RAB) and fire service still kept under siege another militant den in the northeastern town.

Officials earlier suspected some four militants were holed up inside the hideout while they launched simultaneous operation in two dens calling it "Operation Hit Back". 

Islam announced end of security operation at the den on the outskirts of Moulvibazar but added that siege to the other den nearby was still underway while the militants lived in both the houses as tenants with a Bangladeshi-origin British national being owner of the both.

Police's Special Weapons and Tactics (SWAT), backed by other police units including elite Rapid Action Battalion (RAB) and fore service enforced the siege.

Police yesterday simultaneously laid the siege to two Moulvibazar dens and raided an identical hideout at Kotbari, on the outskirts of Comilla.

Senior police officials, meanwhile, said in Dhaka that preferred to wait until tomorrow to launch the assault on the militant's Comilla den as the district town was witnessing mayoral elections today. 

"In consultation with the election commission, we have decided to keep under siege their Kotbari hideout (on the outskirts of Comilla town) for today ahead of launching the expected assault, so the polling process remains undisturbed," a police spokesman told BSS.

The development came two days after army commandos wrapped up their "Operation Twilight" in Sylhet after a five-day security siege to a hideout there.

But Six people, two being police officers, were killed in militants retaliation outside the den ahead of deaths of all their four fellow militants, holed up inside.

Police suspected one of them to be Musa, chief of Neo-JMB, which carried out the deadly July 1, 2016 attack on a Dhaka cafe leaving 22 dead, 17 being foreigners.