Dhaka attack
Terrorists killed 20 people at the Holy Artisan café in Dhaka, Bangladesh on 1 July 2016.Mahmud Hossain Opu/Getty Images

The father of a British man being interrogated by Bangladeshi police in relation to the Dhaka attack has said that his son might have been acting under threat. Abul Hasanat Reza Karim, a British civil engineer, was among the hostages to be released from the café siege on 1 July but has since been in custody for three days.

Police picked up the man after his driving license was allegedly found in the pocket of one of the gunmen who was killed during the attack. Karim has also been filmed talking with the Dhaka terrorists on the restaurant's terrace and inside the building during the siege.

His father, Rezaul Karim, told bdnews24: "The terrorists killed many there with arms. Hasanat saw what they can do. Several videos of Hasanat have been uploaded. He might have been forced to do those things with a gun pulled on him."

Rezaul Karim urged the police to release his son while they carry out a full investigation, adding that they should seize his passport if necessary. He also demanded that hostages who had survived the siege should be questioned to determine his son's role during the attack.

Reza Karim was born in Bangladesh but moved to Britain as a teenager. He graduated from Queen Mary University of London in June 1989 but has since moved back to Bangladesh. It remains unclear whether he is being treated as a terrorist suspect.

His father Rezaul Karim has denied media reports that his son had been fired from North South University for links to banned militant group Hizb-ut Tahrir. He said that his son was not radical and was working for him as a director at his construction firm Basic Engineering Limited.

Isis claim responsibility but may not have been involved

Rezaul Karim said: "Hasanat is not orthodox. He did not pray or fast regularly. He only joined Juma prayers. I don't know whether he is involved with any banned organisation at the North South University."

The Islamic State (Isis) terrorist group claimed responsibility for the attack that killed 20 people at the Holy Artisan café on 1 July. However, authorities have dismisses the link to Isis and insisted that Jamaeytul Mujahdeen Bangladesh (JMB), a local banned militant group, was behind the terrorist attack.