KARACHI - Initial investigations of Tuesday's Hyderi Market blast revealed that Lashkar-e-Jhangvi's Shuja Haider group was involved in the attack.

Around five to eight kilograms of explosive material was used, Federal Investigation Agency's (FIA) special unit claimed. "The explosive material contained around 500-800 ball bearing," the FIA unit added.

At least seven people, including a three-month-old baby, a 12-year-old girl and a woman, were killed and 22 others injured – the victims predominantly belonging to the Dawoodi Bohra community – when twin blasts rocked a neighbourhood in North Nazimabad on Tuesday evening.

Police claimed that LeJ's members Mohammad Shaqib Farooqi, Murtaza alias Shakil, Arab Miskeen, Murad Shah and several others were involved in Tuesday's twin blasts. Police also detained two brothers of one of the suspects involved in the blast.

The suspected LeJ members were also involved in three blasts in 2009 – one in Orangi town on Muharram 8 and another at Paposh Nagar, Chandni Chowk, on Muharram 9 and the third at Light House on Muharram 10.

Suspects were arrested from Maripur Road in 2010 but they escaped from the city courts when their accomplices attacked the police with hand grenades.

Talking to media representatives, Karachi West Deputy Inspector General (DIG) Naeem Akram said that Tuesday's blast had similarities with the Chinese Consulate blast of July 23, 2012.

Senior police official Aslam Khan said investigators suspected the Bohra community was the target of the blasts as they own many of the shops and houses in the area. "They are peaceful community that live in tens of thousands in Karachi and mainly do business. We are investigating why they have been targeted," he said.

Bohras said to be by some quarters as an offshoot of the minority Shia Muslim group, but they regard themselves as quite distinct and follow different customs. Karachi, Pakistan's largest city, is plagued by sectarian, ethnic and political violence, with at least 1,100 dying in attacks this year, but this is thought to be the first time Bohras have been successfully targeted.

However, a police investigator speaking anonymously said officers foiled an attempted bombing in Hyderi Market just weeks earlier.

"Just a month ago, we recovered a powerful bomb in the same area," he said. "They are peaceful people and we are seriously investigating sectarian reasons behind the explosion." "The community is reasonably afraid because of the attack, but we are intensifying security in the area."

Many of Pakistan's Bohras – who number half a million, according to community leaders – are traders, and around half live in Karachi, running food, grocery and clothing businesses. "We are very peaceful people, such attacks have highly shaken our confidence. We are in a state of shock and the government will have to do a lot to restore our confidence," Naveed Lotia, 42, a cloth merchant in Hyderi said.