A Pakistani army officer says soldiers raided the headquarters of a well-known political party in Karachi, arresting about 20 suspects, seizing weapons and sealing the premises.

Col. Tahir Mahmood says troops seized a large cache of assault rifles and detained the suspects — including six "known criminals" — in the raid early Wednesday at the Muttahida Quami Movement's offices in the heart of the city.

He claims the party sheltered criminals and obstructed life in the neighborhood by placing barricades in the streets.

The MQM is a prominent party that controls most of Karachi but is often accused by opponents of using violence to bolster its power. Its leader, Altaf Hussain has lived in exile in Britain since 1992.

Party official Farooq Sattar condemned the raid as politically motivated.