Nigeria must step up its measures to prevent further spread of the deadly bird flu virus, the UN has warned.
People have rushed to sell poultry at market before restrictions bite
The government needs to clamp down on the trade in poultry and intensify culling and movement controls, said two UN world bodies.
Nigerian officials have confirmed the virulent H5N1 strain of the virus is affecting poultry in three states.
Chickens started dying four weeks ago, leading to fears that the emergency measures may come too late.
The Food and Agriculture Organisation and the World Organisation for Animal Health also urged neighbouring Benin, Cameroon, Chad, Ghana and Niger to tighten border inspections.
The agencies said they would send a joint mission to Nigeria within 48 hours to assess the situation.
The World Health Organization (WHO) has called for a massive public education campaign, to stop bird flu from spreading to humans in Nigeria.
The WHO says it is also sending experts to Nigeria who will use a mass polio vaccination from Saturday to help detect possible human cases of the virus.
"All countries must take measures to protect human health against avian flu and prepare for a pandemic," WHO director general Lee Jong-Wook said.
The deadly H5N1 strain of bird flu was found on three more farms in the north of the country on Friday, where thousands of poultry have died recently.
The new cases - confirmed by National Veterinary Research Institute head Doctor Lamy Lombar - are in Kano State and Plateau State, on either side of Kaduna, where the first case was found on Wednesday.
Samples have now been sent abroad for further analysis.
The WHO's regional director in Africa said international support had arrived but most of it in the form of technical advice and not what the region needs most - money.
Police marksmen, ordered to cull 180 ostriches at a farm in the virus-stricken north, killed only 120 birds before running out of bullets, the Associated Press news agency reported.
Although the government said it will compensate farmers if their poultry are killed, people have been rushing to sell sick or dead chickens in the markets before restrictions are imposed.
It is not clear how the virus has spread to Nigeria. It was first found in South-East Asia and more recently Turkey and Russia.
Some experts blame illegal poultry imports; others migrating birds.
More than 80 people have died of H5N1 bird flu since the disease's resurgence in December 2003 - most of them in South-East Asia.
Experts point out that cross-infection to humans is still relatively rare, and usually occurs where people have been in close contact with infected birds.
But they say if the H5N1 strain mutates so it can be passed between humans, it could become a global pandemic, killing millions.