Ho Peng Kee, Singapore's senior minister of state for law and home affairs, opened a three-day conference hosted by Interpol for government officials, police and health experts to explore ways of preventing and dealing with a bio-terrorist threat.

''We may not realize that a biological attack has occurred until perhaps days or even weeks later,'' Ho said in the keynote speech.

''By that time, the terrorist may already have fled the country or succumbed to the biological agent, and all the valuable investigative leads may have disappeared,'' Ho noted.

The al Qaida-linked Jemaah Islamiyah (JI), a terrorist group blamed for a spate of attacks and plots throughout Southeast Asia, has relied on bombings, including suicide bombers.

A manual discovered in the Philippines in 2003, however, indicated interest in acquiring chemical and biological agents.

The JI has been held responsible for the 2002 Bali nightclub attacks that killed 202 people, last October's attack on the island that left 20 dead and several attacks in Jakarta.

With the ease of air travel, Ho warned the impact of a bio-terrorist attack could spread from country-to-country by infected victims.

Singapore passed a law in 2005 carrying a life-imprisonment term for anyone using biological agents for non-peaceful purposes.

As a close ally of the United States, the city-state regards itself as a prime target of terrorists and has uncovered plans to attack its infrastructure, transport facilities, the US and Israeli embassies.

The US has been urging Asian countries to enact tougher laws against bio-terrorism.