"The suicide explosion 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 as we laid the siege to the den," Monirul Islam, the chief of police's counter terrorism unit, told reporters.
He said the blast was so powerful that it tore the bodies into pieces, making it difficult for the police to ascertain exactly how many people were inside the militant den in Moulvibazar Sadar upazila, Nasirpur.
The militants in the hideout belonged to Neo-Jamaatul Mujahideen Bangladesh (Neo-JMB), inclined to Islamic State.
The neo-JMB was behind the July 1 terror attack on a Dhaka cafe that killed 22 people, including 17 foreigners.
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The police today launched 'Operation Hit Back' to flush out militants from their hideouts after they failed to convince them to surrender.
Islam said the police entered the house after a drone was flown into the den to assess the situation and found out that "the entire family committed suicide, finding no way to flee the security siege".
He said that the two couples led a secretive life and even barred the children from interacting with neighbours.
Islam said Special Weapons and Tactics unit, backed by elite anti-crime Rapid Action Battalion (RAB) kept under siege another Islamist den in the northeastern town.
Today's operation was launched two days after the chief of neo-JMB, a terror outfit linked to the country's worst attack in Dhaka, was killed along with three terrorists in 'Operation Twilight' in Sylhet.
IS has claimed several attacks in Bangladesh, but the government rejects the presence of foreign terrorist groups in the moderate Muslim-majority country, blaming home-grown groups such as the neo-JMB for terrorist attacks.
Bangladesh has been witnessing a spate of attacks on secular activists, foreigners and religious minorities since 2013. The country launched a massive crackdown on militants specially after the Dhaka cafe attack.
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