A powerful aftershock rattled the quake-devastated Armenian city of Leninakan on New Year's Eve, killing at least six people and briefly disrupting relief efforts, a spokesman for the official Armenian Press Agency said Tuesday. The spokesman said an aftershock measuring 6 on the 12-point Soviet scale struck Leninakan, once a town of about 280,000 people north of Yerevan. He said six deaths had been confirmed.