Hasnat Karim, a Bangladeshi British national and Tahmid Khan, a student at the University of Toronto have been arrested in the capital of Bangladesh on Thursday (4 August) on suspicion of involvement in the Dhaka cafe siege last month.

"We can confirm that they were arrested under Section 54 of CrPC (criminal procedure)," police spokesperson A.K.M.Shahidur Rahman was quoted as saying by AFP. The police can detain someone on suspicion of any crime under this law.

Rahman added that they had applied for permission to hold Khan and Karim in custody for 10 days but there had been no response to their application.

Local media reports said that both of them were being interrogated for suspicious behaviour during the siege. Khan was reportedly seen holding a firearm and Karim was strolling with the attackers.

When gunmen stormed into the Holey Artisan Cafe on the night of 1 July, killing 20 people, Khan and Karim were allegedly inside the cafe. However, both of them were not seen in public since the siege ended. The families of men have said that they are no more than innocent bystanders. They stressed that there was no evidence to link them to the attackers.

Karim, 47, was a professor at the North-South University in Dhaka. He left the university in 2012 and had been working as a director at his father's engineering firm. The 22-year-old Khan, was back in Bangladesh, after a leave from his University in Canada. Earlier this week, police named Tamim Chowdhury, a Canadian citizen as the mastermind of the attack.

The attack on the Holey Artisan Bakery was the deadliest in the country and the Islamic State (Isis) had claimed the responsibility. However, Prime Minister Sheikh Hasina insisted that the attack was mounted by home grown Islamists and denied the presence of terrorist groups like Al-Qaeda and IS (Daesh).