Members of Bangladesh Police Detective Branch (DB) escort a man, center, whom they have identified as Shariful Islam Shihab, a former member of the banned Islamic group Harkatul Jihad, on May 15, 2016. (AP Photo)

Bangladesh police have rounded up 3,155 people in just 24 hours after the country's prime minister vowed to catch `each and every killer' responsible for the recent uptick in brutal murders of bloggers, Hindus, Christians, LGBT activists, and other minorities claimed by violent Islamist extremists.

The Islamic State claimed responsibility for three murders last week, all of which targeted religious minorities. Hindu monastery worker, Nitya Ranjan Pandey, 60, was walking in the northwestern district in Pabna early on Friday morning when he was attacked by unidentified assailants.

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

According to SITE Intelligence, a US-based monitoring group, IS also claimed responsibility for the hacking deaths of an elderly Hindu priest and a Christian shopkeeper. They also claimed the murder of a counter-terrorism police official's Muslim wife.

Militants have killed more than 30 people in Bangladesh since February last year. IS have claimed responsibility for 21 of those attacks since their first claim in September last year. The local al-Qaeda branch has claimed most of the rest.

However, the government has consistently denied that IS is present in Bangladesh, and says domestic militants are responsible.

Bangladesh police said there were 37 suspected "Islamist militants" among the 3,155 people arrested in the past 24 hours. They also say they arrested hundreds of potential criminals who had warrants against them.

Police told the Associated Press that none of those arrested are believed to be "a high-level operator" organizing the attacks. All detainees are being held in jail.

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, an outlawed group that authorities believe are partly 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.