Indonesian experts say the number of fowl culled and inoculated by the health authorities lags far behind the total infected, which can not cut the chain of the highly pathogenic H5N1 virus transmission.

"The millions of chickens being killed is a lot, but proportionally, it's not so much as to cut the chain of virus transmission," Indonesian Veterinary Association chairman Budi TriAkoso said.

On Wednesday, the government claimed it had culled almost 29 million fowls and vaccinated more than 260 million chickens over the last two years, in response to international criticism that it had been unwilling to carry out mass culling.

The chairman said as bird flu is found in almost all part of the country, infecting many of the country's estimated one billion chickens, so the number of culled fowl in the country was small.

"That's why we keep seeing new cases of bird flu emerge," he was quoted on Saturday by the Jakarta Post as saying.

Budi added that the government could not claim success on its poultry vaccination drive because field workers use eight different kinds of vaccine.

"The government should choose just one type," he suggested. "The more vaccines we use the more likely they are to endanger other creatures."

Animal experts believe that the use of a variety of vaccines to curb the spread of H5N1 among animals might cause certain strains of the virus to become more robust and resistant to vaccines.

I Putu Widhiantara, a communication officer for the Food and Agriculture Organization (FAO), which is partnering with the Agriculture Ministry in addressing bird flu outbreaks, believes there is still much to be done to cut the chain of H5N1 transmission among poultry.

"According to data from the National Commission on Bird Flu, Indonesia has 435 million chickens living in backyard farms," he said. He added that most of the H5N1-infected fowl were found in backyard farms.