But Minister of Health Siti Fadillah Supari said authorities were yet to determine how a government official and his two young daughters living in a Jakarta suburb contracted the virus.

All three died earlier this month, but the official's wife and son have not shown any signs of the disease.

``We will still investigate and do surveillance,'' Supari said, but ``until now we don't know the cause.''

World Health Organization representative Georg Petersen said in Jakarta: ``It is an alarming situation. It shows us that most countries can get this infection, and we need all to be alert and prepared.''

Avian influenza, which arrived in Asia in late 2003, has so far also killed 40 people in Vietnam, half of them since December, 12 in Thailand and four Cambodians.

Health authorities fear the virus will mutate and become easily passed between humans, which could cause a global pandemic. Supari said a pig farm 15 kilometers from the victims' home had been reported infected by flu in April, and slaughter of sick animals had taken place.

But not all of the animals had been destroyed, she admitted. People should be vigilant but not panic.

Separately, Agriculture Minister Anton Apriyantono asked parliament's approval on Thursday for 52 billion rupiah (HK$41 million) in emergency funds to stop the disease from spreading.

When announcing Wednesday that the three deaths were linked to bird flu, Supari said the virus had not mutated and there was no need to worry about human-to-human transmission.

WHO's Petersen said Thursday: ``We have not seen any infection spreading outside intimate family contact. So we don't say it's a human to human transmission.''

Authorities have taken samples from more than 300 people who had contact with the family. They also plan to carry out extensive tests on animals within a 20km radius of the family's house and slaughter those infected.

Jakarta residents expressed mixed feelings. ``I wanted to move earlier, but I don't know where,'' said 31-year-old Frina Cahyadi, who lives near where the deaths occurred.

Housewife Luwi, munching on a chicken curry, thought authorities had the situation in hand. Anyway, ``killer diseases do not only come from chicken. Life and death are God's will.''

Last month, Indonesia, the world's fourth most populous country, reported its first human case in a poultry worker, but the man did not develop symptoms and remains healthy.

Agriculture ministry experts have reported sporadic H5N1 virus outbreaks killing more than nine million fowl in 21 provinces, out of a total of 33, across the archipelago since late 2003.

Indonesian policy has favored vaccinating over culling to stop bird flu, due to lack of funds to compensate farmers.

The WHO has questioned the effectiveness of vaccines and say culling is the best weapon.

The virus has already jumped species in Indonesia and was discovered in pigs in May on densely populated Java island.