PHNOM PENH - Bird flu has killed a 12-year-old boy in Cambodia, the impoverished Southeast Asian nation's sixth victim, the World Health Organization (WHO) said on Wednesday.

The boy, from the southeastern province of Prey Veng, abutting Vietnam, died on Tuesday night, said Michael O'Leary, the WHO representative in Phnom Penh.

He said a laboratory in the capital confirmed the boy was infected with the H5N1 avian flu virus.

Six Cambodians have died of bird flu since the H5N1 virus first emerged in Southeast Asia in late 2003. The 12-year-old's death is the second this year.

Last month, a 3-year-old girl died of the disease. The girl lived in a village in Kampong Speu province about 40 miles (60 km) west of Phnom Penh.

Most Cambodian outbreaks have occurred in provinces abutting Vietnam, which remains the hardest hit country in terms of human deaths, but Kampong Speu is in the middle of the country, showing the virus was spreading.

Before the latest death, 191 people were known to have been infected with H5N1 worldwide since 2003, of whom 108 had died, the WHO has said.

Last week, a government minister said tests confirmed the H5N1 virus in dead ducks near Cambodia's border with Vietnam.

"This makes us worried that the virus will spread to other areas because of our poor health system and bad communications," Deputy Agriculture Minister Yim Vanthoeun told Reuters last Thursday.

The H5N1 virus remains mainly a disease of poultry, but could spark a pandemic in which millions could die if it mutates into a form that spreads easily from person to person, the WHO says.