Pakistan confirmed on Tuesday the H5N1 bird flu virus in samples taken from poultry flocks late last month.

The samples from two flocks in North West Frontier Province were sent to a laboratory in Britain. The flocks, totalling around 23,000 birds, have since been culled, and officials say they have not found any other incidents of bird flu.

"I can only confirm that the H5N1 type of virus was found in chickens from both the farms," Agriculture Ministry official Mohammad Akhlaque told Reuters.

"I don´t have more details," he added.

Speaking to Geo News television channel, Livestock Commissioner Muhammad Afzal said there had been no other cases of bird flu discovered since the outbreak was first reported on February 27 at farms in Manshera and Abbotabad -- two towns in NWFP province.

"We have already taken all necessary precautionary measures. We are continuously watching," Afzal said. "As soon as we see any outbreak elsewhere we will deal with it."

Pakistan had been bracing for bad news from the British laboratory because the highly pathogenic H5N1 virus had already been identified in neighbouring Afghanistan, India and Iran.