Facebook posts suggest some of the militants who attacked a Bangladesh restaurant, killing 20, were educated young men from well-to-do families.
Bangladeshi police are looking to social media as they try to confirm the names of Islamist militants who attacked the Dhaka restaurant.
Islamic State posted pictures of five fighters it says were involved in Friday's killings in Dhaka's diplomatic zone, most of the victims from Italy, Japan, India and the United States.
"Let the people of the crusader countries know that there is no safety for them as long as their aircraft are killing Muslims," it said in a statement.
Posts on Facebook identified three of the five, whose grinning images appeared in front of a black flag, as Nibras Islam, Rohan Imtiaz and Meer Saameh Mubasheer.
Some of the men went to an elite public school in Dhaka, Scholastic, and then college at North South University in the capital and Monash University in Malaysia, according to the posts.
Masudur Rahman, deputy police commissioner of Dhaka police, said officers are probing those links.
"A majority of the boys who attacked the restaurant came from very good educational institutions. Some went to sophisticated schools. Their families are relatively well-to-do people," Bangladeshi Information Minister Hasanul Haq Inu told India's NDTV.
Police have said all six gunmen killed were locals and five were on a government militant watchlist.
Friday's attack marked a major escalation in scale and brutality by militants demanding Islamic rule in Bangladesh, whose 160 million people are mostly Muslim.
Police arrested a seventh man at the restaurant who they suspect played a role in the attack. He is currently in hospital.
Home Minister Asaduzzaman Khan believes home-grown militants responsible for a wave of killings against minority groups in the past year and a half were to blame for Friday's bloodshed.
