BEIJING, Aug. 4 -- Premier Li Keqiang on Monday urged the rescue of people as top priority in relief work after a deadly 6.5-magnitude earthquake hit southwest China's Yunnan Province.

Li gave the instructions aboard a plane rushing to the quake zone, where at least 398 people died as of 2 p.m. Monday.

The quake occurred at 4:30 p.m. Sunday (Beijing Time) with a depth of 12 km. The epicenter was at Longtoushan Township, 23 km southwest of the county seat of Ludian.

The earthquake was the worst to jolt the region in the last 100 years, causing higher-than-expected losses.

There is no time to delay the rescue, Li told senior officials of the central government departments as well as the People's Liberation Army and the Armed Police at an emergency meeting held on the plane.

He urged the greatest efforts to search for the missing and rescue those buried under the debris.

"(We can) never give up until the last minute," he said.

Rescuers must be highly cautious against secondary disasters to prevent more casualties, as the possibility of strong aftershocks of five to six magnitude cannot be ruled out, he said.

He also called for all-out efforts to treat the injured and transfer those suffering serious injuries to hospitals in nearby regions with better medical conditions.