Southeast Asia has been on guard since the 2002 Bali bombings that were blamed on the Jemaah Islamiya network, a group linked to Usama bin Ladin's al-Qaida.
"We should not underestimate because in this region there is a growing chemical industry," said Kazuhiro Nakai, director of the biological and chemical weapon conventions division at Japan's Foreign Affairs Ministry.
"Secondly, we have a local terrorist network here," he told reporters after a security conference in the Malaysian capital Kuala Lumpur. "They are linking with international terrorist organisations, including al-Qaida."
Support for US policies in Iraq from countries in the region such as Singapore has heightened fears that the region may be vulnerable to more attacks.
Singapore foiled a plan in 2001 by Jemaah Islamiya to smuggle three tonnes of ammonium nitrate - nearly the amount used in the 1995 Oklahoma City truck bomb that killed 168 people - across Malaysia's border for attacks on Western targets in Singapore.
"We should not underestimate because in this region there is a growing chemical industry"
director, biological and chemical
weapon conventions, foreign affairs ministry, Japan
"There are three elements to take into consideration," said Shinsuke Shimizu, director of international counter-terrorism cooperation at Japan's Foreign Ministry, citing the chemical industry and "terrorist" alliances.
"The third element is the huge consequences that might occur if actually there is a chemical terrorist attack," he said.
Implementation of the Chemical Weapons Convention would help reduce the threat of chemical terrorism, Nakai said after the seminar that brought together experts from Southeast Asia, China, Japan and South Korea.
Under the 1993 Chemical Weapons Convention, countries agreed to abandon such weapons. A total of 161 states have signed so far.