The H5N1 bird flu virus has been confirmed at another Pakistani poultry farm, an Agriculture Ministry official said today.
Authorities confirmed outbreaks of the H5N1 virus at two poultry farms in the Northwest Frontier Province (NWFP) in February.
The new outbreak was discovered on a farm near the capital, Islamabad.
"It was an small farm and we have already destroyed a total 3,500 chickens there," Mohammad Afzal, the ministry's livestock commissioner, told Reuters. Pakistan has had no human cases of the disease.
The virus has spread across Asia, into parts of the Middle East, Africa and Europe since 2003. Scientists fear the virus could mutate into a form that jumps easily between people and starts a global flu pandemic.
While only 194 people are known to have been infected so far worldwide, about 109 have died. However, scientists say millions of people could be infected in a human pandemic but with a much lower mortality rate.
Mr Afzal said workers at the farm where the new outbreak was detected would be tested. "We have informed the National Institute of Health about the strain and now they will carry out tests of the workers at the farm," he said.
All poultry on farms within five km (three miles) of the outbreak would be strictly monitored, he said.
The H5N1 virus has been found in Pakistan's neighbours including Afghanistan, India and Iran.