China deployed thousands of rescue workers including military personnel and dispatched aircraft, helicopters and earth digging machinery to the quake-hit Yunnan province on Monday as the death toll crept to the 400 mark.
Rescue and relief work was hampered due to heavy rain, landslides, damaged buildings and roads and the constant fear of aftershocks, which could potentially trigger more buildings to topple.
The terrain in the affected area is anyway mountainous besides being remote.
Till Monday evening, at least 398 people in Ludian area of Yunnan in southwest China were confirmed dead. Nearly 1900 were injured, some of them critically.
More than 2.3 lakh residents have been evacuated, state media reported. More than 12000 houses had collapsed and more than 30000 damaged.
The quake had shaken the region on Sunday afternoon at around 4.30pm, triggering sudden death, panic and chaos.
Considered among the poorer and heavily populated regions in China, the earthquake disrupted electricity supply and telecommunication facilities in the area.
Quoting official figures, state media said each square kilometer of Ludian houses an average of 265 people, twice the provincial average, according to official figures.
"Ludian is recognised as especially poor by the Chinese government, which includes the county seat on its state-level poverty list," Xinhua, China's official news agency, said in a report.
Till Monday, about 33,000 tents, 10,000 quilts, 60,000 cotton coats, 10,000 folding beds, 10,000 sleeping bags, 5,000 sets of folding chairs and tables as well as 50 mobile toilets have been dispatched, said a statement from the ministry of civil affairs.
Though the region lies in a quake-prone area, near a fault-line, buildings have been constructed in the towns without adhering to safety standards.
According to the state media, weak buildings were one of the reasons behind the damage and death toll.
"The severe damage and death toll caused…have been blamed by Chinese authorities on the fragility of local buildings, the area's dense population and the quake's shallow epicenter," Xinhua reported.
"Most rural houses in the county were made of brick or wood, were not designed to be resistant to quakes, and many of them were outdated," the China Earthquake Administration said in a statement.
Premier Li Keqiang visited the disaster-hit areas on Monday and monitored the rescue and relief operations being conducted.
Earlier, Li instructed officials and officers of the People's Liberation Army to carry out rescue work without delay, adding that an unified command system should be established so that demands raised during the quake relief can be met effectively.