Islamic State has claimed responsibility for stabbing a Christian to death in Bangladesh.

The group said Hussein Ali was killed as a "lesson to others", an online group that monitors extremist activity said.

Three attackers approached the 68-year-old on a motorbike while he was taking his regular morning walk in the town of Kurigram and then stabbed him in the neck. He had been aware of the dangers he faced, once telling a member of staff from Redcliffe College in Gloucester: "They don't know anything, they don't understand, forgive them." He prayed that God would "place me under Your control".

Bangladesh has seen a surge in Islamist violence in which liberal activists, members of minority Muslim sects and other religious groups have been targeted.

According to the US-based SITE Intelligence Group, Islamic State said on Twitter that a "security detachment" killed the "preacher" to be a "lesson to others".

Kurigram district police chief Tobarak Ullah said three men were picked up for questioning after the attack.

Over the last few months, Islamic State has claimed responsibility for the killings of two foreigners, attacks on members of minority Muslim sects and other religious groups, but police say domestic militant group Jamaat-ul-Mujahideen was behind the attacks.

At least five militants of Jamaat-ul-Mujahideen have been killed in shootouts since November, as security forces have stepped up a crackdown on militants seeking to make the moderate Muslim nation of 160 million a Sharia-based state.

Additional reporting by Reuters.