Moslem students marched in several cities Monday to denounce the United States because of a book they consider blasphemous and to protest the killing of five people in rioting Sunday. Hundreds of police stood guard in Islamabad near the U.S. Information Center, which was stormed by nearly 3,000 Moslem fundamentalists Sunday. Five people were shot to death, 83 people were injured and at least 65 people were arrested in the three-hour melee.