Dhaka: Bangladesh police came under grenade attack when they raided two suspected extremist hideouts on Wednesday, days after a major anti-militant drive in which 10 people were killed.

Police said counter-terrorism officers raided two houses in  Moulvibazar district in the northeast after receiving a tip-off that extremists were sheltering there.

A stand-off ensued, with those inside the houses throwing grenades, local police chief Rashedul Islam told AFP.

"In one of the houses, we suspect there are eight to nine of them," he said, adding the houses were owned by a Bangladeshi-origin British citizen.

The raids came after army commandos stormed a five-storey building in the nearby city of Sylhet, triggering a violent three-day stand-off.

At least four extremists died and another six people including two police officers were killed when two bombs went off on Saturday near a crowd watching the operation.

The Islamic State group claimed the twin bomb attacks but the government has rejected the claim, instead blaming a banned homegrown Islamist organisation.

There has been a resurgence of extremist attacks in recent weeks in the Muslim-majority nation of 160 million after a relative lull since five IS-linked gunmen killed 22 people including 18 foreign hostages at a Dhaka cafe on July 1.

IS has also claimed at least two of three other incidents this month in which attackers blew themselves at security checkpoints, including one targeting an elite security force tasked with tackling Islamist militancy.

Analysts say Islamist militants pose a growing danger in conservative Bangladesh, where a long-running political crisis has radicalised opponents of the government.

Bangladesh prides itself on being a mainly moderate Muslim country. But that perception has been damaged by a series of gruesome killings of atheist bloggers, foreigners and religious minorities.

Since the cafe attack, security forces have launched a nationwide crackdown on Islamist extremist groups, killing around 60 suspected militants.

These include the founders of a new faction of the banned Jamayetul Mujahideen Bangladesh, which has been blamed by authorities for most attacks.