Thailand's Prime Minister Thaksin Shinawatra has admitted that his government suspected an outbreak of avian flu about two weeks ago.
The Thai PM is accused of a cover-up
Mr Thaksin told reporters he had decided not to tell the public until Friday to avoid causing mass panic.
He has ordered troops to help a cull of chickens to stop the disease spreading.
Bird flu has spread to two more regions of Thailand while Indonesia revealed it too had an outbreak, though officials there said it had not spread to humans.
Amid growing criticism of its handling of the disease, Thailand has invited other Asian nations hit by the crisis to an emergency summit this week.
European Union and Japanese officials will also be invited to the meeting in Bangkok on Wednesday, as well as the World Health Organization (WHO) and UN food agency.
After weeks of speculation, Thailand - Asia's largest poultry exporter - admitted the presence of the disease two days ago and confirmed that it had spread from poultry to humans.
Several countries subsequently banned imports of poultry from Thailand, including its main customers, Japan and the EU.
On Sunday, China announced it was banning chicken imports from Thailand and Cambodia, which has also been hit by a bird flu outbreak.
Two Thai boys are infected, while the death of a 56-year-old Bangkok man who raised fighting cocks is thought to have been caused by the virus.
On Sunday, the Thai prime minister visited the worst-hit province of Suphan Buri, where officials are moving from farm to farm destroying all poultry.
AVIAN FLU ALERT
First jumped "species barrier" from bird to human in 1997
In humans, similar symptoms include fever, sore throat, and cough
Types known to infect humans are influenza A subtypes H5N1 and H9N2
Mr Thaksin told reporters the government had taken precautionary measures, despite keeping quiet about its concerns.
"We have suspected this for about a couple of weeks" he said.
Government under fire
The BBC's Rachel Harvey in Bangkok says that politically as well as economically, everything now depends on how quickly the virus can be brought under control.
She says ordinary Thais are questioning whether the government is telling them everything, even now.
AVIAN FLU TIMELINE
Nov 2003 - Thailand reports what it calls chicken cholera
15 Dec - S Korea confirms avian flu outbreak
9 Jan 2004 - UN sends help to Vietnam after avian flu outbreak
11 Jan - First of five Vietnamese deaths confirmed as avian flu
13 Jan - Japan confirms avian flu outbreak
15 Jan - Taiwan announces different strain of avian flu
21 Jan - Laos reports suspected chicken cholera
23 Jan - Thailand confirms first human cases of avian flu
23 Jan - Cambodia detects first case in chickens
The government has come in for strong criticism from the media, while opposition politicians are threatening a motion of no confidence.
Deputy leader of the opposition Democrat party, Abhisit Vejjajiva, said it would be "unacceptable" if the government had misled the public.
"We understand that... no government would want the public to panic, but I think the problem was the route that the government took meant that people who were at risk, who have direct contact [with chickens], did not take the necessary precautions," he said.
"Now we have a few people who are infected, some of whom are already dead."
The worst-hit country in the region is Vietnam, where six people have died of avian flu.
The WHO has warned that the Asian outbreak could mutate and become more dangerous.
Avian flu has also affected chickens in Cambodia, Indonesia, Taiwan, Japan, and South Korea - but is not known to have jumped from birds to humans in these countries.