A four-year-old boy has died of bird flu in Indonesia, the health ministry said Tuesday, the 10th fatal case in the country this year.

The boy, from Bogor district in western Java, died on December 6 after a week of high fever.

"He contracted the H5N1 (bird flu) virus from playing with chickens at his home," Rita Kusriastuti, head of animal-borne infectious diseases at the ministry, told AFP.

Health officials said last week they had identified a more virulent strain of the H5N1 virus in the country that has killed hundreds of thousands of ducks in recent weeks.

Indonesia has been hardest-hit by bird flu, with 159 fatalities reported since 2003 out of 359 worldwide, according to World Health Organization figures, which exclude the latest death.

Bird flu typically spreads from birds to humans through direct contact, but experts fear it could mutate into a form that is easily transmissible between humans.