Seven people have died and a woman is in intensive care after undergoing kidney dialysis treatment at a hospital in northern Vietnam.

The incident happened at Hoa Binh Province General Hospital, west of the capital Hanoi, on Monday.

A group of 18 were receiving treatment when some felt sick and breathless. Six patients died on Monday afternoon and another one later that night.

The health ministry has launched a criminal investigation.

“I would like to apologise to families and the whole community, we are very surprised at this rare incident,” hospital director Truong Quy Duong told state media.

The 18 patients were receiving routine dialysis, a process that cleans the blood and removes waste products – often by passing blood through a machine – for those whose kidneys stop working properly.

Le Tien Dung, whose wife is in intensive care, told AFP news agency that his wife had fallen ill during the treatment.

“She became itchy all over her body, she had a stomach ache and vomited,” he said. “My biggest hope is that my wife will overcome this.”

The remaining 10 patients have been transferred to hospital in Hanoi and are reported to be in stable condition.

State media said Deputy Prime Minister Vu Duc Dam had visited the hospital and called for “all available resources” to help the surviving patients.

Health ministry officials were at the hospital and must report findings by the end of today, it said.