The worst cold spell in years, linked to icy winter weather in neighbouring China, has seen hospitals overflow with cases of pneumonia and other respiratory diseases, health officials and media reports said.

The unusual cold spell has killed more than 8,000 cattle and buffalos, wiped out over 50,000 hectares (120,000 acres) of rice fields and devastated peanut and soybean crops, the agriculture ministry said.

Northern farms have been hard hit as temperatures dropped below freezing and ice covered mountains in northern Lang Son province and around the former French hill station of Sapa in Lao Cai province near the Lao border.

At least two children's deaths have been linked to the harsh weather, when they froze to death during a family motorcycle trip in Phu Tho province north of Hanoi this week, the state-run Vietnam News daily reported.

"This cold spell has lasted for 33 days," said Bui Minh Tang, director of the National Centre for Hydro-Meteorological Forecasting. "This is the coldest and longest cold spell in more than a decade.

"It has caused human and economic losses, cattle have died, rice crops have died, some people have died, and many have fallen sick."

Another official at the meteorological centre added: "We predict that this long cold spell will end by Sunday."

The number of children admitted to hospital has tripled in some areas, and many elderly have been treated for pneumonia, with hundreds of people in hospital across northern Vietnam, local media reported.

"The number of children coming to our clinic increased because of the cold weather," said Nguyen Tien Dung, head of paediatrics at Bach Mai Hospital in Hanoi. He said admissions had at least tripled to 30 to 40 children a day.