Prolonged heavy rain triggered a landslide that has killed three people in northern Quang Ninh province.

The deaths raised safety fears for thousands of residents in the flood and landslide-prone northern mountainous provinces of Ha Giang, Lao Cai and Yen Bai as the wet season approaches.

Seventeen people were killed or presumed dead after floods and landslides in Ha Giang province in the first seven months of this year. Forty-two houses were also destroyed.

The province's Xin Man, Yen Minh, Bac Quang and Quang Binh districts were particularly prone to floods and landslides, officials said.

To Thanh Lai, chairman of Yen Thanh Commune People's Committee in Quang Binh district, warned that landslides were expected at numerous locations along Highway 279.

Floods and landslides killed 238 people in Lao Cai province between 2000 and 2008, swept away 1,200 houses and destroyed more than 10,000ha of paddy fields.

Le Thanh Du, the provincial Agriculture and Rural Development deputy director, said: "Floods and landslides have occurred more frequently and been more serious in recent years," adding that thousands of residents were put at risk annually.

He blamed climate change for the unpredictable weather.

"In previous years, flash floods and landslides were often caused by prolonged heavy rain of between 200-300mm, but this year, floods and landslides have taken place in areas where the rainfall has measured just 8-10mm," he said.

"As a result, local authorities have been carrying out more checks in high-risk areas to ensure response measures are prompt. They have also relocated more than 5,000 people from areas prone to flash floods and landslides," Du said.

Le Thanh Hai, deputy director of the National Hydro-meteorological Forecasting Centre, said it was difficult to predict exactly where and when landslides and flash-floods would take place.

"The lack of flood-forecasting technology and limited training hinder our work. Reliable warnings are based on many factors, not just on the likelihood of rain," he said.

He said that flash floods and landslides often happened after spells of drought, particularly in mountainous areas and near river mouths.

"When hearing strange noises and finding that the water level in rivers has dropped suddenly or risen dramatically, people should move to safe areas," he said.

Hai added that heavy rains were expected in northern mountainous regions in the next few days./.