Authorities in Beijing have issued the country's second-highest warning for rainstorms and the highest for floods, with the downpours expected to last into Tuesday morning.

In Hebei province, which encircles the capital, the heavy rains caused a landslide in a village near the city of Chengde, state broadcaster CCTV said.

Four were killed and eight are still missing, it said, with the national emergency management department dispatching a team to inspect the "severe" flooding in the province, where a further two died over the weekend.

Over 4,600 people were evacuated over the weekend in Fuping County, while in neighbouring Shanxi province, one person was rescued and 13 were missing after a bus accident, state media said.

Footage from the broadcaster showed roads in the province and a crop field submerged in rushing water on Sunday.

In Beijing, over 4,000 people in suburban Miyun district were evacuated due to torrential rains.

The area's reservoir "recorded its largest inflow flood" since it was built more than six decades ago, state media reported.

On Monday in Mujiayu, a town just south of that reservoir, AFP journalists saw the reservoir release a torrent of water.

Power lines had been swept away by muddy currents while military vehicles and ambulances ploughed through flooded streets.

A river had burst its banks, sweeping away trees, while fields of crops were inundated with water.

Some roads were badly damaged, with chunks of exposed concrete scattered across lanes and twisted guardrails lining their sides.

The low-rise houses in the mountainous area, though mostly intact, were surrounded by gushing floods.

- Extreme weather -

China's National Development and Reform Commission has allocated 50 million yuan ($7 million) to assist relief efforts in Hebei, with the funds going to post-disaster emergency recovery and construction of infrastructure, Xinhua news agency said.

Natural disasters are common across China, particularly in the summer when some regions experience heavy rain while others bake in searing heatwaves.

China is the world's biggest emitter of the greenhouse gases that scientists say drive climate change and contribute to making extreme weather more frequent and intense.

But it is also a global renewable energy powerhouse that aims to make its massive economy carbon-neutral by 2060.

Flash floods in eastern China's Shandong province killed two people and left 10 missing this month.

A landslide on a highway in Sichuan province this month also killed five people after it swept several cars down a mountainside.