Explosives used in the crude bomb explosion in the capital’s Gulistan on Monday night were poor in quality, but the manufacturing technique was different from that of conventional crude bombs.

A battery was found attached to the bomb in a manner previously seen adopted by extremist groups, said investigating officials of the Counter Terrorism and Transnational Crime (CTTC) unit.

Analysing the size of the bomb and the incident spot, the officials further said they were suspecting the bomb might have been planted before as its size meant it would have been hard to throw.

Besides, the force of the blast created a hole in the ground and scattered bricks which suggest it might have been planted.

The bomb exploded at 7:35pm injuring two policemen and a community policeman.

Hours into the explosion, SITE Intelligence Group, an American company that tracks online activity of white supremacist and jihadist organisations, said the Islamic State claimed responsibility for the attack.

“For the first time in over two years, the IS claimed credit for an attack in Bangladesh, bombing policemen in the capital, Dhaka,” the organisation added.

Meanwhile, Dhaka Metropolitan Police (DMP) Commissioner Asaduzzaman Mia said the anti-terrorism experts of the CTTC unit were analysing the credibility of the IS claim.

“We are also checking the claim using our cyber crime team and we can only say something about it after investigation,” said the DMP chief.

He came up with the statement while talking to reporters after visiting the injured policemen at Dhaka Medical College Hospital (DMCH).

Asked about the bomb, the DMP boss said it was slightly different from regular crude bombs. “Our bomb disposal unit and CTTC officials have already visited the spot and collected evidence, and analysed the injuries.

“We are analysing every possible detail and action will be taken against those responsible,” added the DMP boss.

Bangladesh is not out of the sphere of influence of worldwide global extremism efforts but local militant groups had no capacity to conduct any large and organised violence here, he said.

Meanwhile, a sub-inspector of Paltan Police Station filed a case in connection with the blast against some unidentified people under the Explosive Substances Act, said Shiblee Noman, additional deputy commissioner of DMP (Motijheel zone).

No one was arrested till filing of this report yesterday night.

A police high official investigating the case told this newspaper that they were not able to collect the evidence properly as it was damaged by locals before they reached the spot.

“We tried to collect the Close Circuit Television Camera footage but did not find any that directly covered the spot. There was a camera on the spot but it was found damaged,” the official said, requesting anonymity.

The bomb exploded five minutes after traffic constables sat on the spot to take rest. This was around five minutes after the electricity in the area went out, said locals and investigators.

While visiting the spot yesterday, this correspondent saw the hole created by the blast and the damage it did to nearby trees.

The two traffic constables injured in the explosion -- Nazrul Islam, 45, and Mohammad Liton, 42, -- were shifted to Rajarbagh Police Line from DMCH, said the inspector of DMCH police outpost.

Meanwhile, five to six unknown people were made accused in a case filed in connection with the raid that left two suspected militants dead in the capital’s Bosila yesterday.

Rapid Action Battalion (RAB) filed the case with Mohammadpur Police Station early yesterday against the two dead “militants” and three to four unknown people, said Rab-2 Commanding Officer Ashique Billah.

The suspected militants were killed after they allegedly detonated an improvised explosive device in a house in the area during the raid.

“The two dead are still unidentified and we are trying to identify them using DNA tests. We have already sent samples to the DNA laboratory of Criminal Investigation Department,” Billah said.

They were not able to collect fingerprints as the fingers of the dead were completely burnt, he added.

“We are investigating the case and trying to trace the other associates.”