Bangladesh's security forces killed four members of a Islamist militant group on Saturday blamed for on attack on a cafe in Dhaka in July in which 22 people were killed, mostly foreigners.

The four militants, believed to be members of Jamaat-ul-Mujahideen, were killed in two raids by Bangladesh's Rapid Action Battalion (RAB) on militant hideouts on the outskirts of the capital, Dhaka, RAB spokesman Mizanur Rahman Bhuiya said.

The July 1 attack in Dhaka's diplomatic quarter was claimed by the Islamic State militant group and was one of the most brazen in Bangladesh, which has been hit by a spate of killings of liberals and members of religious minorities in the past year.

The government has blamed domestic militant groups but security experts say the scale and sophistication of the July attack suggested links to a trans-national Islamist network.

Police have killed more than two dozen suspected militants in shootouts since the Dhaka cafe attack, including its presumed mastermind, Bangladesh-born Canadian citizen Tamim Ahmed Chowdhury.

The United States believes elements of Islamic State are "connected" to operatives in Bangladesh, US Secretary of State John Kerry said during a visit to Dhaka in August.

Nine Italians, seven Japanese, an American and an Indian were among those killed in the July attack.