Anti-terrorist police have uncovered a large cache of explosives and firearms in the northeast English city of Hull that they believe were stored for a terrorist campaign across Europe, Scotland Yard said. Detectives arrested an Arab who was believed to be living in the apartment where the explosives were found. News reports said the Arab was a member of the Palestine Liberation Organization, but police would not comment. Officers seized 68 pounds of explosives, four assault rifles, seven hand grenades and bomb-making equipment. The seizure came as police hunted suspects who shot and seriously wounded an Arab cartoonist in London last month.