The Vientiane outbreak is the only known case in Laos while Nakhon Panom is 300 km (200 miles) to the southeast.

Lao Foreign Ministry spokesman Yong Chanhthalansy said there had been no reports of outbreaks across the border from Nakhon Panom and criticised Bangkok for suggesting a link to the Thai cases.

"Those remarks were made by irresponsible and uncouth officials," he told Reuters by telephone. "Under the current critical circumstances, we should work together to solve the problem, rather point fingers at one another."

The farm in Vientiane, where about 2,500 chickens died earlier this month, according to Lao state media, also had an outbreak in early 2004 when the virus swept through parts of Asia, including Laos, where most of the 5.6 million people live in remote, rural areas.

FAO bird flu expert Laurence Gleeson said he was trying to find out if the Thai and Lao outbreaks were related.

We do not know whether the recurrence of avian influenza in some parts of the poultry in the two countries is a result of low-grade circulation of the virus in backyard farms, or a reintroduction from outside," Gleeson said.

"A lesson learnt from the outbreaks in the two countries is that the animal health surveillance system needs to be reviewed," said Gleeson, who is due to arrive Vientiane on Tuesday.

Thailand has tried to step up its defences against bird flu following the return of the virus after an eight-month lull and the death of a 17-year-old youth in the northern province of Phichit.

Adopting an extra cautious stance, health officials have placed more than 800 people involved in culling in Nakhon Panom or in hospitals in the area on a bird flu watch-list.

The Agriculture Ministry also banned imports of poultry and equipment from neighbouring countries, with violators facing a maximum penalty of 2 years in jail and/or a 40,000 baht ($1,000) fine.

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