HANOI, April 1 (Reuters) - Bird flu has been found on a duck farm in southern Vietnam, the first outbreak of the disease in the country since early March, the Agriculture Ministry"e;s Animal Health Department said.

Tests showed the presence of the H5N1 virus in ducklings at two farms in the southernmost province of Ca Mau. A total of 65 ducklings had died from the disease since March 22, the department said in a report seen on Sunday.

The ducklings had not been vaccinated against the virus, the report said.

The agriculture ministry said last week it would vaccinate up to 90 percent of all poultry to prevent bird flu returning during winter, the season when the virus seems to thrive best.

Vietnam has had no human cases of bird flu since November 2005.

But the H5N1 virus flared up in the south late last year, spreading to several provinces, despite stern government measures to control it.

Experts fear the virus could develop the ability to spread easily from person to person. If it does, millions could die around the globe. For the moment, though, it remains largely a disease in birds.

The World Health Organisation says bird flu is known to have killed 170 people, most of them in Indonesia and Vietnam, since late 2003.

The virus has killed 42 people in Vietnam and 71 in Indonesia.

Experts and government officials said poultry vaccinations had helped prevent the H5N1 virus spreading in Vietnam. About 12 million birds, mainly ducks and chicken, have been vaccinated so far this year, the Animal Health Department said.

Hanoi has been importing bird flu vaccines for poultry from China and the Netherlands and the Agriculture Ministry expects to import 500 million doses this year and next.