Five motorcycles were also badly damaged during the 20-minute clash.

Law enforcers have been deployed in and outside the BNP office at KD Ghose Road to avoid further clashes.

The injured -- Khulna city JCD President Masud Parvez Babu, BL College JCD President Ershad Hossain Dablu, former vice-president of Khulna Polytechnic Institute JCD Golam Mostafa, Joint Secretary of city unit of Shechchhasebak Dal Golam Mostafa and activist Sajib -- are undergoing treatment at Khulna General Hospital. They received multiple stab injuries during the clash.

Both the rival factions lodged FIRs with Khulna Police Station yesterday. But the police could not arrest anybody.

One faction is led by M Nurul Islam MP and the other by city BNP convenor Ali Asgar Lobi.

According to witnesses, the clash took place when JCD supporters loyal to Ali Asgar prevented some leaders loyal to Nurul Islam from entering the BNP office.