Police fired tear gas at demonstrators who attempted to put up pictures of wounded Lebanese civilians at a Holocaust memorial in this northern Greek city, authorities said. The incident occurred late Tuesday as about 500 protesters from a Communist-backed trade union marched to protest Israel's bombardment of Lebanon. A group of protesters challenged police at the memorial site and were pushed back when police responded with tear gas and pepper spray. No one was arrested and there were no reports of injuries. In Athens, a small demonstration Tuesday at the Israeli Embassy ended peacefully.