DHAKA: The self-styled Islamic State (IS) militant group claimed responsibility for gunning down an Italian citizen on the street in the diplomatic quarter of Bangladesh's capital, according to an intelligence group monitoring jihadist threats.

The claim by the radical Islamist group could not immediately be verified independently, but if confirmed would mark the group's first attack in the South Asian nation.

Police in Dhaka said they had no leads in tracing the three unidentified assailants who, riding on a single motorcycle, drove up alongside Italian citizen Tavella Cesare and shot him Monday night.

"We have no idea, we can't say anything definitively for now," police official Mukhlesur Rahman said, declining to comment on the IS claim of responsibility. "Let the investigation happen."

Witnesses said the attackers fled the scene after Cesare fell to the ground, according to police. Cesare was taken to a nearby hospital, where doctors declared him dead.

His colleague Alo Rani Dhali said Cesare had come to Bangladesh in May to work in the food security sector for a Netherlands-based church cooperative called ICCO.

In a statement dated Monday, the IS reportedly said a "security detachment" had tracked and killed Cesare with "silenced weapons" in Dhaka, according to the SITE intelligence group's website.

It warned that "citizens of the crusader coalition" would not be safe in Muslim nations. Almost 90 per cent of Bangladesh's 160 million population practices Islam.

Dhaka police were questioning witnesses including street beggars who allegedly heard the gunshots and saw the attackers flee, local broadcaster Somoy Television said Tuesday.