HANOI, Oct 24 (Reuters) - Bird flu has killed nearly 300 ducklings in central Vietnam, the second infection found in the Southeast Asian country this month, the government said on Wednesday.

Tests performed by a Vietnamese laboratory confirmed the H5N1 virus had infected 310 ducklings that were nearly two months old, and 290 of them died on Tuesday at a farm in Quang Tri province, the Agriculture Ministry"e;s Animal Health Department said in a report.

Animal health workers were working at the site to contain the virus, it said.

The outbreak is the second detected this month, after officials found the H5N1 virus among ducks in the southern Mekong delta province of Tra Vinh on Oct. 6. None of the infected ducks had been vaccinated against the virus.

Agriculture Minister Cao Duc Phat said earlier this month that bird flu would soon return among unvaccinated birds, especially as the weather cooled in late autumn and winter in northern provinces.

The second phase of vaccination has now been under way in 40 out of Vietnam"e;s 64 provinces and 62.65 million birds have been injected, nearly one third of the country"e;s total poultry stock, the Agriculture Ministry said.

Vietnam"e;s poultry stock has been increasing, with 226 million birds counted at the end of August, 5.3 percent up from a year ago, of which the waterfowl stock expanded 8.7 percent to 68 million, government figures showed.

Bird flu has killed four people among the seven cases of infection in Vietnam so far this year, bringing the death toll since late 2003 to 46.

Globally, the H5N1 virus has killed 203 people out of 331 known cases, with most of the deaths in Indonesia, Vietnam, Thailand and Egypt, the World Health Organisation said.