Two powerful bombs went off at separate places near a militant den in Sylhet, killing five people, including two policemen, and injuring 40 others, even as joint forces were raiding the hideout for a second straight day yesterday.

Police suspect the bombs were hurled by the cohorts of the militants holed up inside the den at Atia Mahal, a five-storey building in the city's Shibbari.

The explosions occurred in the evening during an Army-led operation, codenamed “Operation Twilight.”

It's unclear how many militants are inside or if any of them were killed in the raid by the army commandos who began the operation around 9:20am yesterday, some 32 hours after police cordoned off the building around 1:30am on Friday.

Talking to The Daily Star early today, Rab-9 Commanding Officer Ali Haider Azad Ahmed said the first blast was “an attack,” but he could not say who carried it out.  

After the explosion, law enforcers found a bag while raiding the surrounding areas. Suspecting that there were bombs inside it, they called in the bomb disposal unit but the bomb exploded suddenly, he said.

Hours after the blasts, US-based SITE Intelligence said terror group Islamic State claimed credit for the attack.

“The Islamic State's Amaq News Agency reported that the group is responsible for a bombing on Bangladeshi forces in Sylhet,” SITE said on its website.  

The Bangladesh government denies that IS has presence in the country.

Earlier in the day, Para Commandos from Sylhet division evacuated 78 residents who had been trapped inside the building since early hours Friday.

Police tracked down the hideout barely a week after busting two militant dens in Chittagong.

Briefing reporters about Operation Twilight around 6:30pm, Brig Gen Mohammad Fakhrul Ahsan said, “Our prime objective, as directed by the prime minister, was to rescue those who had been trapped inside the building. With the mercy of Allah, we have been able to rescue all the 78 residents safely.”

Army personnel take a family to safety after evacuating residents from the building yesterday afternoon. Photo: Sheikh Nasir

Those rescued include 30 men, 27 women and 21 children. The building has about 150 rooms in some 30 flats. And the militants were constantly changing their position inside the building, he said.

He added the operation was taking some time as they were handling the situation with extreme caution, since the militants planted explosives and Improvised Explosive Devices (IEDs) in different rooms as well as the staircase.

An injured person in a Rab flak jacket arrives at the emergency department of Sylhet Osmani Medical College Hospital in the evening. Photo: Star

He could not say exactly when the operation would end.

“The 10 to 12 loud bangs you heard were actually explosions of IEDs inside the building by the militants,” he said. “We can't say right now how many terrorists are there.”

 Since the operation began yesterday morning, all eyes had been on the green building, which has two units.

The commandos reached the scene around 8:00am following recommendations from an army observation team that went there on Friday to assess the situation.

The first of the gunshots were heard around half an hour after the operation started.

People hurt in two explosions outside Atia Mahal are being taken to hospital. Photo: Star

Witnesses said the army commandos went to the roof of the building from an adjacent four-storey building to evacuate the residents.

Later around 2:04pm, armoured vehicles of Bangladesh Army broke through the boundary wall of the building, reports our Sylhet correspondent.

Sporadic gunshots and explosions were heard till 5:00pm, although it was not clear who were firing the shots.

At least two injured army members were seen being taken out of the building.

Several thousand locals gathered near the building and on the rooftops of nearby buildings since the morning.

Law enforcers disconnected gas connections to the building before the operation began. The power connections were snapped on Friday.

Militants, including a woman, were inside one of the six flats of the building's ground floor in Pathanpara's Shibbari area, police said.

Akhtar Hossain, officer-in-charge of Jalalabad Police Station, said, around 1:30pm on Friday, the female militant suspect yelled from a window of the flat: “Bring SWAT quickly because you [police] won't be able to do anything to us… We don't have much time.”

Later, SWAT team and bomb disposal unit of counterterrorism unit went there from Dhaka.

Around 6:30am on Friday, the militants threw a grenade at police from their flat. Police then fired blanks.

Law enforcers couldn't enter the building on the first day as the militants blocked the entrance to the building with a refrigerator, with bombs attached to it.

It was for the first time after last year's Gulshan attack that army commandos have been called in to take on militants.

THE ATTACKS

The first bomb went off all of a sudden on Sylhet-Fenchuganj road in Gutartik area around 7:00pm, minutes after the briefing by the Brig Gen Ahsan.

The site of this attack is about 400 metres north of Atia Mahal, owned by Ustar Ali, a businessman.

Two people -- Wahidul Islam Opu, a college student in South Surma Upazila, and an unidentified man -- died in this attack, police and hospital sources said.

“When we were coming out of the briefing, we suddenly heard a bang. First we thought it came from the building. But we soon noticed people running here and there in panic,” said our Moulvibazar correspondent.

Several people were seen lying in a pool of blood on the blast scene. Some were trying to help the injured while others fled for their lives. Within moments, the crowded area was deserted.

The second blast came around an hour later, this time close to Atia Mahal, killing three people, including two police officials, and injuring many, police said.

The dead are Chowdhury Abu Mohammad Kaiser, an inspector of court police in Sylhet, Monirul Islam, inspector (investigation) of Jalalabad Police Station, and Shahidul Islam of Dariapara in Sylhet city, police said.

The injured, including several law enforcers, were rushed to Sylhet MAG Osmani Medical College Hospital.

Rab intelligence wing director Lt Col Abul Kalam Azad and Major Azad of Rab headquarters were among the injured.

They were flown to the Combined Military Hospital in Dhaka, Brig Gen Md Ruhul Amin, director of the hospital in Sylhet, told this correspondent.