Four militants were killed in Chapainawabganj extremist den at Shibnagar Trimohoni in Shibganj of Chapainawabganj on Thursday.
Rajshahi range deputy inspector general of police M Khorshed Hossain at a news briefing informed newsmen about the death figure.
Among the dead, all male, there are Jamaatul Mujajideen Bangladesh leader Rafiqul Islam Abu.
Khorshed Hossain said all of them died from suicidal explosion.
Police also recovered the wife of Rafiqul Islam Abu and their daughter. They were admitted to Chapainawabganj General Hospital.
Earlier, sound of blasts and sporadic gunshots were heard at regular intervals from the den as Special Weapons and Tactics continues its operation.
TM Mojahidul Islam, superintendent of Chapainawabganj Police, said the team started its operation, codenamed 'Eagle Hunt', around 9:15am.
The SWAT team urged the 'extremists' through a loudhailer to surrender around 12:30pm and around 4:00pm but they did not respond.
The operation at the 'extremist den' was postponed for technical reasons on Wednesday night.
The SWAT team of the Counter Terrorism and Transnational Crime under Dhaka Metropolitan Police started the operation around 6:45 pm on Wednesday.
The police super said 4-5 big explosions took place at the house as the 'extremists threw' four grenades at the law enforcers after the operation had begun on Wednesday.
The CTTC suspects that there are 3-4 extremists, including one Abu, in the house.
Locals claimed Abu along with his family members rented the house two and half months ago introducing him as a spice vendor.