More than 250,000 people have been evacuated from their homes in northern China after the worst floods to hit the country in decades inundated villages and towns, authorities said.

Torrential rains caused the Yalu river, which forms the border between China and North Korea, to breach its banks and overflow in both countries.

Chinese officials said on Sunday the number of people displaced by the rains in Liaoning province had more than doubled in 24 hours.

Thousands of people in North Korea were also forced to flee to safer grounds.

In the northern Chinese city of Dandong alone, floods forced out more than 94,000 people as floodwaters destroyed power and transport links, state media reported.

Rescue operations

The floods killed at least four people on Saturday in Kuandian county, which is around 100 kilometres northeast of Dandong. A couple in their 70s and a mother and son died when flash floods swept away their homes, China's official Xinhua news agency cited a local flood-control official as saying.

A 60-year-old man was also missing in Kuandian after his house collapsed in a rain-triggered landslide.

The government has launched a rescue operation, which included dispatching helicopters to airlift people stranded on rooftops of flooded homes.

China's national meteorological centre, meanwhile, warned on Sunday that new downpours were expected in various areas of Liaoning, for another 24 hours at least.

Nearly 3,900 people have been killed or left missing this year in flood-related incidents across China, official figures show.

In the northwestern province of Gansu, a mudslide on August 7 crashed into homes in the remote town of Zhouqu, leaving at least 1,434 people dead and another 331 missing.

Also, in the southwestern province of Yunnan, rain-triggered mudslides killed at least 23 people and rescuers are still searching for 69 others who went missing. 

North Korea evacuations

In neighbouring North Korea, more than 5,000 people have been moved to safety after areas of Sinuiju city were "completely inundated", the official Korean Central News Agency said.

Traffic in downtown Sinuiju was "paralysed" and flood victims were stranded on rooftops and on hills.

The deluge prompted Kim Jong-Il, the North's leader, to order an emergency rescue operation.

North Korea has been hit by widespread flooding this summer, which has washed away homes, roads, railways and farmland, according to state media reports from Pyongyang, the capital.

After decades of deforestation, North Korea is particularly vulnerable to flooding.

In 2007, it was reported that at least 600 people had been killed or went missing from devastating floods.

PHOTO CAPTION

Farm houses in North Korea are seen submerged in floodwaters near the Sinuiju area in North Pyongan province near the border with China.

Al-Jazeera