The militants at Atia Mahal were expert bomb makers and the Improvised Explosive Devices (IEDs) found in the Sylhet den were all homemade, investigators have said.
The detonators of the IEDs were assembled in various militant hideouts in Sitakunda of Chittagong and then brought to the Sylhet den. And the nitrate gel used as explosive was smuggled into the country through Chapainawabganj border from a neighbouring country where the substance is used for mining, multiple investigators told The Daily Star.
The fact that militants were getting hold of the substance came to law enforcers' notice after a police checkpoint came under attack in Comilla on March 7, and the subsequent arrest of two terror suspects, they said asking not to be named.
Officials of the Counter Terrorism and Transnational Crime (CTTC) suspect that large consignments of the gel entered Bangladesh in recent months.
In the past, militants used to smuggle the detonators into the country, but now they have learnt to make those at home, said an official, referring to the expertise and training of the militants who holed up inside Atia Mahal.
Police first encircled the five-storey building at Shibbari around 1:30am on Friday on information that some militants assembled a large cache of explosive there.
Army commandos then launched an operation codenamed “Operation Twilight” on Saturday morning that came to an end yesterday afternoon, when the army handed the crime scene over to the police.
Announcing the conclusion of the 110-hour standoff, one of the longest anti-terror offensives, Military Intelligence Director Brig Gen Fakhrul Ahsan said the militants there were highly equipped and trained. They even fitted bombs on a refrigerator and a motorcycle and placed those at the entrance of the building, making it difficult for the commandos to enter the den.
“The entire building has become highly risky as they placed explosives in the staircase and different other places,” he told reporters at Sylhet's Jalalabad Cantonment in the evening.
The army disposed of about 10 IEDs from the first, second and third floors yesterday, he said, adding that a more meticulous search would be needed as there were more explosives there.
Four militants, including a woman, were killed during the commando assault.
Four civilians and two police officers also died in a twin bomb attack on Saturday night near Atia Mahal. Terror group Islamic State claimed responsibility for the bombing.
WAS MUSA THERE?
Talking to this newspaper, investigators said they primarily thought one of the four was Maynul Islam Musa, a key leader of the militant outfit “Neo JMB”.
However, there is no official confirmation yet.
According to police, Musa was trying to reorganise the outfit and carry out targeted attacks.
Police claim “Neo JMB” is an offshoot of the banned militant outfit Jama'atul Mujahedeen Bangladesh (JMB), which carried out several large-scale attacks in 2001-2005.
Musa has become a key leader of “Neo JMB” following the killing of its top leaders, including Tamim Chowdhury, Maj (retd) Jahid and Tanvir Kaderi, in separate operations in Dhaka and Narayanganj, CTTC unit chief Monirul Islam, said on January 7.
Autopsies on the bodies of two militants sent to Osmani Medical College morgue were done yesterday and police collected visceral, DNA and finger prints, said Sohel Ahmed, officer-in-charge of Kotwali Police Station in Sylhet.
Morgue sources said there was no trace of food in the bodies and the body of the woman was completely charred except the toes.
Meanwhile, police in their inquest report said the two died during Sunday's assault.
The male militant died after detonating his suicide vest while the female militant killed herself by setting fire to her body, Khairul Fazal, officer-in-charge of Moglabazar Police Station, said citing the inquest report.
The two are aged between 25 and 32, the report said.
MOVING TO HINDU AREAS?
Of late, key “Neo JMB” leaders have been renting houses in Hindu neighbourhoods in bordering areas to avoid suspicion, said CTTC officials.
As part of their new strategy, the terrorists have also decided that they would destroy their dens with explosives when detected by law enforcers, they added.
The group has been constantly shifting and relocating in different regions in the wake of frequent raids in the capital and elsewhere in recent months.
INSIDE ATIA MAHAL
The militants rented a four-room flat on the ground floor in January identifying themselves as Kawsar and Marzina. The man said he was an auditor at a private company.
On impacts of the explosions for the past few days, some walls between the rooms have collapsed. Plasters are all falling from the ceiling and walls while all furniture burned. The entire flat is riddled with bullets, shells and blood, law enforcers said.
After all the four militants were killed by Monday, bomb disposal experts started disposing of bombs from yesterday morning. Four explosions were heard around 10:30am.
The operation actually ended on Monday, but the army took yesterday to keep searching for explosives.
Members of other law enforcement agencies and as many as 70 firefighters also took part in the operation.
Meanwhile, life in Shibbari and adjacent areas is slowly returning to normal as residents started coming back to their homes yesterday.
Kunjo Lota, 60, of Bandarghat near Shibbari, was seen returning home with her two grandchildren and a baggage around 4:30pm. She along with other family members left their house on Sunday and took shelter in the house of a distant kin around one kilometer away.
Vagiroti Paul, 40, of Pattya Para village, left home with her husband and son after one of their neighbours was hit by a stray bullet during the exchange of fire between the militants and the commandos on Saturday. She returned home yesterday.