The army, which is conducting 'Operation Twilight' on the terror hideout in Shibbarhi at the outskirts of Sylhet city, have taken control of a 3-kilometre area after two explosions in the neighbourhood killed six people on Saturday evening.
Vehicles are not allowed to move in the area as well as pedestrian movement is restricted.
Locals said after a relative lull following the fatal twin blast, heavy gunfire along with blasts could be heard from the spot from 7am. Two large explosions around 10 am and another around 12pm rocked the area.
Early on Friday, Sylhet Metropolitan Police and personnel from police's counterterrorism unit cordoned off the complex.
Army commandos began the assault on Saturday morning to round-off the siege to the complex housing a five-storey and a four-story building.
The two buildings have 30 flats with as many families living in them.
Some reports also suggest that the militants might have planted improvised explosive devices (IEDs) across the buildings to hit the assault group if they tried to storm the buildings.
Commandos rescued 78 civilians from the building on Saturday, who had been stranded for more than 30 hours since police sealed-off the complex.
Getting the civilians to safety appeared to be the first operational priority to avoid unacceptable collateral damage.
Gunfire and explosions could be heard from inside the building in phases on Saturday after the commandos moved in.
Around 5:40 pm, the gunfire and blasts stopped, when the army said civilians have been rescued from the building.
There was no official comment on whether any of the militants were captured or killed at the den. An army spokesperson said that the "operation is not over yet".
Soon after the army's media briefing, two blasts at one end of the street to the building left six persons, including two police officers dead and at least 40 others hospitalised.
The law enforcers killed in the blasts are court police Inspector Chowdhury Mohammad Koysor and Jalalabad Police Station Inspector Monirul Islam.
Both of them were from the police's bomb disposal unit.
Shah remained unidentified until Sunday morning, when relatives identified him at the hospital.
His family said Shah and Islam, who ran a catering business, were friends. The two went to Shibbarhi area on Saturday in connection with a catering contract.
It was not immediately clear whether the Saturday evening's blasts were bomb attacks carried out in support of the militants holed up in the den.
"The blast occurred just after he said that there was red spinach in the bag. Five to six people were injured in the explosion," he said.
"Another large explosion occurred when police and RAB rushed to the scene. Around 25 people were injured in the second blast," he added.
It seems these were 'reinforcement' came for the militants who are cornered by the army commandos in a hideout where the operation is about to be in its final stage.
It was not clear who fired the shots as the media, and curious onlookers have been kept over a kilometre away from the epicentre of commando operations since it began on Saturday morning.
Shibbarhi residents said they did not hear shots or blasts from the complex until 7am on Sunday, when heavy gunfire erupted from the scene and at least three huge explosions until 12pm.