KARACHI, Pakistan, Sept. 22 —The police in Karachi said today that Bengali guerrillas were apparently operating in West Pakistan as well as in East Pakistan.

Newspapers reported today that over the weekend the Karachi police had arrested seven Bengalis suspected of starting a fire aboard a ship here Sept. 13 and “arranging for the disappearance of four fishing trawlers last June.”

The police were also reported to be looking for other Bengalis in Karachi involved in "spreading rumors”, and subversive activity.