The decree called "Urgent Matter Number 11" indicates the North is treating the outbreak as an epidemic, said Good Friends, which has extensive cross-border contacts.

"It indicates North Korea is taking the disease very seriously," group director Lee Seung-Yong told AFP.

The secretive communist nation issued the rare decree to ensure patients receive urgent treatment, he said.

Any vehicles could be stopped anytime to transport patients, regardless of the status of passengers inside, he said.

North Korea this month reported nine cases of the (A)H1N1 virus. But Seoul officials and private groups suspect there are more and that the disease is spreading amid poor health conditions.

Good Friends said Tuesday that about 50 people have died.

In one case, it said in a newsletter, a naval base at Ongjin, 80 kilometres (48 miles) southwest of Pyongyang, ceased all training after a 19-year-old soldier was infected with swine flu.

South Korea's unification ministry, in charge of cross-border relations, said it had no information on the current situation in the North. The World Health Organisation said it had not been informed of any deaths.

The world body said it had sent medication and equipment to help stem the outbreak and assess the scope of infections.

"However, we have not received any information from North Korea regarding deaths," Khanchit Limpakarnjanarat, a surveillance epidemiology adviser at the WHO's regional office in New Delhi, told AFP.

Observers say the virus could pose a particular threat to the North because of public malnutrition amid persistent food shortages and a lack of drugs.

On December 18 the South shipped swine flu medication worth 15 million dollars to the North, enough to treat 500,000 people.

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