Dhaka: The terrorists involved in the Dhaka cafe massacre were all young men from affluent families and had studied in elite schools in the city, sources in the Bangladesh government said on Sunday.

The men were all aged 20 or 21 years old and were students of Dhaka's North South University, the sources told CNN-News18 in Dhaka.

All of them had passed out of top-notch schools in the city like Scholastica and the Turkish International School, confirming concerns that students from elite educational instituions were being lured into terror.

Meanwhile, Islamic State released names and pictures of men whom they claimed were behind the attack and warned even more severe attacks on citizens of "crusader countries."

The names given were Abu Omar, Abu Salmah, Abu Rahim and Abu Muharib Al-Bengal. The names and pictures were yet to be confirmed by the Bangladesh government.

The claim comes even as Home Minister Asaduzzaman said the jihadists were not from ISIS but members of the banned local militant group Jamaeytul Mujahdeen Bangladesh.

"They have no connections with the Islamic State," Asaduzzaman told AFP adding that all the attackers came from wealthy families.

"They are all highly educated young men and went to university. No one is from a madrassa," the minister said.

22 foreign nationals, including an Indian girl, were hacked to death by the terrorists after they stormed a restaurant in an upmarket Dhaka locality on Friday night. Hours later Bangla police commandos gunned down six of the terrorists and arrested and interrogated the seventh one.