The Food and Agriculture Organisation (FAO) said on Thursday it was worried about general bans that include countries believed to be free of the deadly H5N1 strain, which has decimated poultry stocks and killed at least 62 people in Asia.
"Trade restrictions to safeguard human and animal health should be imposed only in proportion to the risk involved," the Rome-based agency said in a statement.
"Countries arbitrarily banning the import of poultry products from non-infected countries are increasing the vulnerability of international global markets to price shocks," the FAO added.
It did not name any specific countries that have introduced excessive bans, but countries such as Senegal, Argentina and Sudan have halted all poultry imports, regardless of origin.
Global fears over the potential for a massive flu pandemic are mounting, now that the virus has spread to Europe and Russia.
Governments across Asia on Thursday redoubled their efforts to combat bird flu.
China said on Thursday that it was doing all it could to prevent the spread of bird flu, as a health official said a 12-year-old girl who died in a village that suffered an outbreak had tested negative for the virus.
In Bangkok, Thai Prime Minister Thaksin Shinawatra said bird flu would be on the agenda at a regional meeting of five Southeast Asian leaders next week, with a view to coordinating efforts to stop the spread of the virus.
"Trade restrictions to safeguard human and animal health should be imposed only in proportion to the risk involved"
The Food and Agriculture Organisation
Malaysia imposed a ban on the import of pet birds after avian influenza was detected in a parrot in Britain.
Vietnam said it wanted to begin negotions with drug giant Roche to begin manufacturing its anti-viral drug Tamiflu, widely seen as one of the best treatments for bird flu in humans.
Meanwhile Australian Health Minister Tony Abbott said Canberra was considering repatriating its nationals using Qantas jets should a global flu pandemic strike, and was mulling whether to close borders in case of a massive outbreak.
In Europe health officials opened a two-day meeting in Budapest on Thursday to address the threat to human health posed by bird flu.
Health officials said most European countries were prepared to fight a possible human flu pandemic and downplayed the risk of people contracting the disease through food.
The H5N1 strain, which has killed at least 62 people in Asia, has recently been found in birds in Russia, Turkey and Romania.
Tests on Wednesday confirmed that the deadly H5N1 strain of bird flu had reached Croatia, which borders Hungary.