The death toll from bird flu in Indonesia has now reached 55, after officials confirmed that a 27-year-old woman had succumbed to the disease.
Bird flu is endemic in poultry in Indonesia
Her death is the third from the deadly H5N1 virus in as many days.
Tests by two laboratories confirmed she had the disease, leading the WHO to confirm the cause of death as bird flu.
Indonesia has the world's highest human death toll from the H5N1 virus, and has registered more bird flu deaths this year than any other nation.
The woman from Central Java province died on Friday, after developing symptoms earlier this month.
The WHO said it was still investigating the source of the virus.
Meanwhile a 11-year-old boy died of the disease in a Jakarta hospital on Saturday, and a 67-year-old woman died on Sunday in Bandung, West Java, according to health ministry officials.
Both were believed to have had contact with poultry before they died, the WHO said.
Bird flu is endemic in poultry across most of Indonesia, and transmission from poultry is the main cause of human bird flu.
But there are fears the virus could mutate to a form which could be easily passed from human to human, triggering a pandemic and potentially putting millions of lives at risk.
Bird flu has claimed the lives of more than 140 people worldwide since late 2003.
Most of the deaths have been in East Asia, but the virus has also spread to Europe, Africa and South and Central Asia.