Artillery shells hit a makeshift hospital in Sri Lanka's northern war zone Saturday, killing at least 64 civilians, a government doctor and a rebel-linked Web site said, amid growing international pressure to safeguard thousands of civilians trapped in the area. The Tamil Net Web site accused government forces of shelling the hospital at Mullivaaykkaal. Military spokesman Brig. Udaya Nanayakkara denied the accusation, saying soldiers were only using small arms as they pushed forward to seize the remaining territory held by separatist Tamil Tigers along a small coastal strip in the island's northeast.