A Bangladeshi politician has spoken of his shock on discovering his son was one of the suspected gunmen who murdered foreign hostages, and said many young men from wealthy, educated families had gone missing.

Imtiaz Khan Babul said he was "stunned" to learn of his son Rohan's involvement in the attack, and that he believed young Bangladeshi men were becoming radicalised online.

His comments came after Bangladesh's home minister said the attackers who stormed the upmarket cafe on Friday night, taking dozens of diners hostage and killing 20, were highly educated and from wealthy families.

"We never imagined this, there was nothing at home, no books or anything to indicate that he was leaning that way. So we had no inkling,"

said Mr Babul, an official with the ruling Awami League party, in an interview with the BBC.

Four of the six terrorists who killed 20 people after they took over a local cafe in Dhaka | Twitter

Mr Babul, whose son was among those killed when Bangladeshi security forces stormed the cafe, said he had shared his concerns with friends in Dhaka.

"When I was searching for my son I found that many other boys are missing. Well-educated boys from good, educated families, children of professionals, government officers," he said.

"I used to share my sorrows with them. We do not know how this is happening."

Six young men were shot dead on Saturday at the end of the all-night siege in a Dhaka cafe claimed by the ISIS group. One was taken alive and is being questioned.

One of those killed may have been an innocent bystander, but among the remaining five are a graduate of Bangladesh's leading private university, an 18-year-old student at an elite school, and Rohan, Mr Babul's son.

Another was a former madrasa student from the northern district of Bogra which is seen as a hotbed of Islamist radicalism.

The government has said all the attackers were members of the Jamaeytul Mujahdeen Bangladesh (JMB), a banned local Islamist group.

Rohan reportedly studied at Monash University in Malaysia after leaving Scholastica, where his mother teaches.

(Feature image source: AFP)