Bangladeshi security forces may have accidentally shot dead an innocent kitchen worker when they stormed a Dhaka cafe where gunmen were holding people hostage, police have said.

Saiful Islam Chowkidar, a pizza maker at the Holey Artisan restaurant, was among six men who were killed by the security forces on Saturday when commandos stormed the eatery to end a 12-hour siege, a senior police official said on Tuesday.

"We killed six people in the restaurant. A case has been registered against five. The sixth man was a restaurant employee," Saiful Islam, a top police official investigating the attack, told Reuters news agency.

"He may not be involved," he said, adding that the investigation was going on.


IN PICTURES: Hostage drama in Bangladesh


Police named five men as attackers in a case filed on Tuesday to allow them to launch official investigations, including questioning families of the gunmen for clues as to what turned them into killers.

The five named in the case filing were Nibras Islam, Rohan Imtiaz, Meer Saameh Mubasheer, Khairul Islam and Shafiqul Islam.

At least 20 hostages, including 18 foreigners, died in Friday night's attack, which was claimed by the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group - a claim denied by the government. 

Nine Italians and seven Japanese were among the dead. The bodies of the seven Japanese hostages  were repatriated on Tuesday.

It was one of the deadliest attacks in Bangladesh, where ISIL and al-Qaeda have claimed a series of killings of liberals and members of religious minorities in the past year.

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Police believe that Jamaat-ul-Mujahideen Bangladesh (JMB), an outlawed domestic group that has pledged allegiance to ISIL, played a significant role in organising the band of privileged, educated young attackers.

Police said they were hunting for six members of the JMB who were suspected of organising the attack.

The JMB has been accused of involvement in many of the killings over the past year and police officer Islam said police were interrogating more than 130 of its members already in custody in the hope of gleaning clues.

"We don't know who is the mastermind behind the attack. We just know that these boys were guided to launch an attack on the restaurant," he said.

In Dhaka, authorities were still holding five of the 13 rescued hostages. All five are Bangladesh citizens.

Dhaka Police Commissioner Asaduzzaman Mia said on Tuesday that authorities were still questioning them, including a former teacher at a private Dhaka university and the son of an industrialist. He declined to provide more details about the investigation.

Source: Agencies