The death of a 16-year-old boy on Tuesday night - almost twoweeks after developing symptoms of the H5N1 virus - has raised concerns overthe country's monitoring standards.

"This is the 23rd out of 24 human outbreaks in China where we weren't forewarned by a poultryoutbreak," Joanna Brent, the World Health Organisation spokeswoman in Beijing, told the AFPnews agency.

Health officials said the boy had no history of contact withdead or sick birds, while no outbreaks of the virus among animals had beenreported in the province.

In most cases elsewhere around the world, the disease hasbeen traced to either an outbreak amongst animals or contact between the victimand dead or sick animals, Brent said.

In the light of the latest case she urged Chinese officialsto strengthen monitoring and surveillance of bird flu among animals.

"This is not consistent with what we are seeing aroundthe world," she said.

Of the 24 patients confirmed with bird flu infections in China since2003, 15 have died.

The last human death was of a 44-year-old woman in eastern China reportedin February.

Scientists say that multiple strains of the diseaseoriginated in southern Chinaand spread elsewhere.

Rising toll

The boy's death brings to 170 the number of people who havedied from bird flu around the world, but does not include the latest deaths in Indonesia.

On Thursday, Indonesiaannounced two more deaths from the bird flu virus, taking its human toll to 69,the highest in the world.

Runizar Ruesin, a health ministry official, said one persondied on Sumatra island while the other in an army hospital in the capital Jakarta.

"They tested positive in the first test," he said,adding a second was being conducted to confirm initial results.

Most human cases in Indonesiahave occurred after contact with sick birds, prompting a ban on keepingbackyard chickens in Jakartain the hope of eradicating human infections this year.