Bangladeshi security forces said on Tuesday they had arrested four women suspected of being members of a home-grown militant group blamed for an attack on a Dhaka cafe last month in which 22 people were killed.

Five young men attacked the upmarket cafe on July 1, an assault claimed by Islamic State. Three of the attackers were from affluent Dhaka homes who had broken off contact with their families months earlier.

Police believe that Jamaat-ul-Mujahideen Bangladesh, a banned group that has pledged allegiance to Islamic State, played a role in organising the group.

The four women were arrested in an overnight raid in the capital, based on information from a regional militant leader who was detained last month, said Rapid Action Battalion spokesman Mizanur Rahman Bhuiya.

"Three of them are students of a private university and the other one is working as an intern in the Dhaka Medical College and Hospital," he told Reuters.

At least seven more people believed to have been involved in the attack had been identified, Monirul Islam, chief of counter-terrorism police, told reporters.

"We have got to know their organisational names but their real names and whereabouts are yet to be identified," he said.

Earlier, police said Bangladesh-born Canadian citizen Tamim Ahmed Chowdhury, 30, masterminded the cafe attack. Analysts say Islamic State identified him in April as its national commander.

Al Qaeda and Islamic State have made competing claims for a series of killings of liberals and members of religious minorities in the country over the past year. The government has pinned the blame on domestic militant groups.