(Reuters) - A magnitude 6.1 earthquake jolted central China early on Thursday, the U.S. Geological Survey said.

China’s official Xinhua news agency said there were no immediate reports of casualties from the tremor, which struck at a depth of 10 km (6 miles) in Menyuan county in Qinghai province.

Phone services in Menyuan, home to around 150,000 people, were operating normally, it said.

Witnesses said many local residents, who fled their homes when the earthquake hit, were spending the night in their cars despite temperatures of minus 20 degrees Celsius, Xinhua added.