Police say they have arrested four members of a banned militant group, including a regional commander, suspected in the killing last month of a university professor in northwestern Bangladesh.

English professor A.F.M. Rezaul Karim Siddique was hacked to death on April 23 on his way to work at a state-run university in the city of Rajshahi.

The attackers used sharp weapons and quickly fled the scene.

Rajshahi Metropolitan Police Commissioner Mohammed Shamsuddin said Tuesday that authorities have arrested four members of the Jumatul Mujahedeen Bangladesh group, including regional commander Maskawath Hasan Sakib, nicknamed Abdullah.

He said Abdullah was captured Sunday night and confessed before a magistrate, leading to the arrests of the three other suspects on Monday.