A six-year-old Cambodian girl has died from bird flu, bringing the country's toll from the deadly virus to nine so far this year, the World Health Organisation said Tuesday.

The girl, from the southern province of Kampot, died in a children's hospital in the capital Phnom Penh on June 28, the WHO said in a joint statement with the Cambodian health ministry.

Her death makes it the deadliest outbreak in the kingdom, topping the eight killed by the illness in 2011.

Tests confirmed the victim had contracted the H5N1 strain of avian influenza, it said.

"There have been recent poultry deaths in the village and the girl was likely to be exposed to sick and dead poultry before she became sick," the statement said.

Cambodia has recorded 34 human cases of H5N1 since 2003, with all but six of them proving fatal.

Authorities have been scrambling to control the outbreak, although scientists have been baffled by the sharp rise in deaths this year.

The virus has killed some 376 people worldwide since a major outbreak in 2003, according to WHO statistics.

It typically spreads from birds to humans through direct contact. But experts fear it could mutate into a form easily transmissible between humans, with the potential to trigger a pandemic.