THOUSANDS OF people are missing, and at least 137 people have died, after mudslides smashed towns in northern China following the heaviest seasonal flooding in over a decade, according to state-run Xinhua News Agency.

Rescue workers in Zhouqu county in Gansu province are frantically trying to find survivors, in sludge as high as two metres. Heavy rains are feared to continue for the next five days.

As many as 2,000 residents are still missing following Sunday night’s mudslide.

Chinese authorities have increased the national disaster relief response level to grade II, the second highest level.

“Torrential rains began to fall at around 10 p.m. Saturday. Then there were mudslides and many people became trapped. Now sludge has become the biggest hinderance to rescue operations. It’s too thick to walk or drive through,” Diemujiangteng, head of the county said, according to Xinhua.

Electricity and clean water supplies have been cut off. The government estimates that county badly needs 400 tonnes of drinking water and 20 tonnes of instant food per day.

So far this year, more than 1,000 people have been killed in floods that have devastated some areas, particularly in central and southern China.

See pictures of the ongoing rescue efforts: