Forty people were killed when a brief but violent hailstorm and torrential rain swept through a mountainous region of northwestern China, the local government said Sunday.

Eighteen others remained missing in Min county, a disaster-prone area of Gansu province, while 87 had been sent to hospital, the county government said in a statement on its website.

Officials said 29,300 people were evacuated after rain and hail battered the county for just 60 minutes late Thursday afternoon.

It "wreaked havoc" on all of the county's 18 townships and affected more than two-thirds of its 450,000 residents, the state-controlled Xinhua news agency reported.

"Roads were blocked, houses collapsed, farmland was destroyed, and the power supply and telecommunications services were disrupted by the extreme weather," the agency said, quoting Xu Guangyao, a senior county official.

Min county is 150 kilometres (90 miles) from Zhouqu county, where a rain-triggered mudslide killed about 1,500 people in August 2010.

Hailstorms in the central province of Hunan have also killed six people and left one missing, according to statistics released by the Ministry of Civil Affairs on Sunday, Xinhua reported.

Since May 8 hailstorms have struck across the province, affecting 3.42 million people, the ministry said. About 64,000 people have been relocated to safer areas and 7,600 houses have collapsed.