Islamic State claimed responsibility for the killing of a Hindu monastery worker who was stabbed to death in Bangladesh, a monitoring service tracking militant online activity reported a day after the slaying.

It was the third killing of a member of religious minorities in the mostly Muslim country that the group has taken responsibility for in the past week.

The claim was carried by Islamic State's Amaq news agency, Site Intelligence Group, a US-based monitoring service, reported on Saturday.

Police said unidentified assailants attacked Nitya Ranjan Pandey, 60, while he was walking in the northwestern district of Pabna early on Friday morning.

"He was found lying in a pool of blood," district police chief Alamgir Kabir said, adding that no one saw the attackers.

Hundreds of suspects have been held across the country after police launched a week-long crackdown on militants after a wave of gruesome killings.

In the past week alone, an elderly Hindu priest and a Christian shopkeeper were hacked to death - both of which Islamic State claimed responsibility for - and the Muslim wife of a counter-terrorism police official was also killed.

Militants have killed more than 30 people in Bangladesh, including members of religious minorities, liberal bloggers and academics, since February last year.

Islamic State has claimed responsibility for 21 of the attacks since its first claim in September last year and Al Qaeda has claimed most of the rest, according to SITE.

The government denies either group has a presence in Bangladesh and says domestic militants are responsible.

Five suspected members of the outlawed Jamaat-ul-Mujahideen were killed in shootouts after the woman was stabbed and shot dead on Sunday.

Last month, police announced 1.8 million taka ($23,000) in rewards for information leading to the arrest of six militants of Ansarullah Bangla Team, another outlawed group they believe is behind the violence.

Analysts say a climate of intolerance in Bangladeshi politics has both motivated and provided cover for perpetrators of religious hate crimes.

The government blames the growing violence on political opponents linked to Islamist parties, that it accuses of seeking to create chaos and prevent courts from going ahead with war crimes trials related to the 1971 war of independence.

The opposition party denies the accusations.

Hindus and Christians make up about 10 percent of Bangladesh's 160 million population.