The shallow earthquake struck Sichuan province on the edge of the Tibetan Plateau just after 8:00 am, prompting a major rescue operation in the same area where 87,000 people were reported dead or missing in a massive quake in 2008.
Eighteen hours after the quake hit Lushan county in the city of Ya'an, the death toll stood at 160, the official Xinhua news agency reported, citing the China Earthquake Administration which said more than 6,700 people had been injured.
At least 10,000 homes were destroyed, the Sichuan government said, as rescue workers searched through the rubble for survivors.
Local seismologists registered the quake at magnitude 7.0 while the US Geological Survey gave it as 6.6. More than 840 aftershocks followed, Xinhua said.
The quake was felt in the provincial capital Chengdu, which lies to the east, and even in the megacity of Chongqing several hundred kilometres (miles) away.
Panicked residents fled into the streets, some of them still in their slippers and pyjamas.
"Members of my family were woken up. They were lying in bed when the strong shaking began and the wardrobes began shaking strongly," said a 43-year-old Chongqing resident surnamed Wang. "We grabbed our clothes and ran outside."
Xia Donghai, 48, a migrant worker in the northern province of Heibei rushed home to Lushan when his family failed to respond to telephone calls.
"I am filled with terror, I do not know what I will find when I return to the family home," he told AFP.
At Lushan People's Hospital a steady stream of ambulances continued to arrive in the early hours of Sunday. Most victims were taken to tents erected in the grounds surrounding the hospital, where doctors treated the wounded.
A two-year-old girl with heavy bandages wrapped around her bloodstained head was brought in as AFP watched doctors attend to her.
"Please. It hurts, don't take it off," she screamed as they began to peel her dressing.
In a nearby tent, a 68-year-old woman with a broken arm spoke of the terror she experienced when the quake struck.
"It was as if the mountain was alive," she told AFP. "Now I have no home to go to. So I don't know what I am going to do."
More than 17,000 soldiers and police had joined the rescue mission and five drones were sent to capture aerial images, Xinhua said, as well as aircraft carrying out rescue and relief work.
Some teams had to contend with roads blocked by debris, state television CCTV reported, while one military vehicle carrying 17 troops plummeted over a cliff, killing one soldier and injuring seven others, Xinhua said.
Rescue teams continued working as night fell, using audio, video and radar equipment as well as sniffer dogs to search for survivors, Xinhua reported.
Firefighters had pulled 91 people alive from the rubble, the news agency said, citing the Ministry of Public Security.
The disaster evoked comparisons to the 2008 Sichuan quake, the country's worst in decades, and President Xi Jinping ordered all-out efforts to minimise casualties, Xinhua said.
-- 'Golden time' for saving lives --
Premier Li Keqiang arrived in Sichuan in the afternoon and took a helicopter to the quake zone. The first 24 hours was "the golden time for saving lives", he was quoted as saying.
Amid the rescue efforts, a 30-year-old pregnant woman surnamed Zhao was pulled out of the rubble along with a young child and sent to hospital for treatment, the People's Daily said on its Weibo account.
A local TV journalist due to get married on Saturday instead turned up for work and a photograph of her holding a microphone in her wedding dress with bright makeup and a corsage was widely circulated online.
Condolences have been flooding in for victims of the quake. Nigerian President Goodluck Jonathan conveyed the "solidarity and sincere sympathy of Nigeria", while European Commission President José Manuel Barroso said his "thoughts and feelings are with everyone who has been affected".
The 2008 Sichuan quake, which struck west-northwest of Chengdu, generated an outpouring of support, with volunteers rushing to the scene to offer aid and then-premier Wen Jiabao also visiting.
But there was public anger after the discovery that many schools fell while other buildings did not, creating suspicion of corruption and corner-cutting in construction.
The deaths of the children became a sensitive and taboo subject in the heavily controlled domestic media and social media websites.
Earthquakes frequently strike the country's southwest. In April 2010, a 6.9 magnitude quake killed about 2,700 people and injured 12,000 in a remote area of Qinghai province bordering the northwest of Sichuan.