A strong, shallow quake shook southwestern China in Yunnan province near the border with Myanmar, while a separate 7.3-magnitude quake collapsed a bridge and caused other major damage in the southern part of Qinghai province.
Although the second shock struck about 1,000km (621 miles) north of the first quake in Yunnan, the two quakes were not related, according to US Geological Survey geophysicist Jonathan Tytell.
The state-run People’s Daily newspaper reported that the Qinghai quake was followed by 453 aftershocks throughout the early morning into midday and injured at least eight people.
No deaths have been reported so far from the province, but the shocks tore up roads and bridges, with one collapsing completely.
The Yunnan province seismological bureau gave the first quake a magnitude of 6.4, adding that it struck 8km below the surface northwest of the city of Dali.
The earthquake caused strong shaking around the city, but Chinese news reports showed relatively little damage in the area.
Three people died and 28 were injured, according to the Yunan province’s publicity department.
In a post on the Chinese social media site Weibo, the China Earthquake Networks Centre (CENC) warned local residents to stay away from buildings following the shock.
Relief efforts were under way on Saturday morning, with the provincial authorities sending emergency rations and tents to the affected areas, and authorities in Qinghai setting up temporary safety shelters due to continuous aftershocks.
Moderate to strong earthquakes are fairly common in China, particularly in the country’s mountainous western and southwestern regions.
A magnitude 5 quake in Yunnan last year killed four people and injured 23, while China’s worst earthquake in recent years struck the mountainous western portion of Sichuan province to the north of Yunnan in 2008, killing nearly 90,000 people.
Additional reporting by AP