DHAKA - A jail guard was shot dead by unidentified gunmen on Monday in front of a prison on the outskirts of the capital Dhaka, a police official said.

The official, who declined to be named, said the motorcycle-borne assailants gunned Rustom Ali, 60, a sergeant inspector of Kashimpur jail, down when he was standing at a tea stall.

The gunmen immediately fled the scene on the motorbike, he said.

The motive behind the killing could not be immediately known.

The attack came days after suspected extremists killed a university professor in Bangladesh's Rajshahi district, some 256 km northwest of Dhaka.

Rezaul Karim Siddiquee, professor of Rajshahi University's English Department, was hacked to death on Saturday by unidentified assailants.