(BBC News with Sue) Montgomery.

In one of the most severe monsoon seasons in Asia for years, the Chinese Prime Minister Wen Jiabao has gone to the western province of Gansu, where huge mudslides

engulf

ed mainly Tibetan communities. More than 120 people were killed. Michael Bristow reports.

The">The landslides began at about midnight, when most people were at home and in bed. Television pictures show how rivers of rock and mud slid down mountainsides following heavy rain. They">They buried buildings in their path. Most of the damage happened in the main town of Zhouqu County in the western province of Gansu. The">The landslides blocked the main river running through the town, and water built up behind these natural dams. The">The river eventually burst its banks and flooded the town. Buildings, several storeys high, were reported to be completely under water.

As a monsoon

drench

es Pakistan, officials say at least 40 people have been killed by landslides in the north. The">The rain has severely

hamper

ed aid efforts in the northwest, and officials say the Swat valley is completely cut off. Gan Rice, who's in charge of US (food)flood relief operations there, said it was difficult to reach those in need.

"The

magnitude

of the disaster is very great. The terrain that we were, we are operating in, it is very

formidable

- very high mountains, very constricted valleys, and clearly weather challenges have been a problem for the last couple days."