Illegal burning on Indonesia's Sumatra island to clear space for palm oil plantations is a chronic problem during the June to September dry season. The smoke has also shrouded neighboring Singapore, which experienced a severe deterioration in air quality over the past few days.

On Sunday, Malaysia's prime minister, Najib Razak, declared a state of emergency in the Muar and Ledang districts of the southern state of Johor. The country's environment minister, G. Palanivel, said the air pollution index in the two districts had exceeded 750, more than double the 300 level that indicates hazardous.

"Prime Minister Najib Razak has agreed to declare emergency status in Muar and Ledang with immediate effect," Palanivel said. Domestic media have quoted him as saying cloud seeding would be carried out in the affected areas in the hope of triggering rainfalls.

Malaysia's rating classifies the air as "unhealthy," differing from Singapore's, which during the week indicated life-threatening conditions for the ill and elderly in the city-state. Levels recorded have exceeded the smog disaster that gripped Southeast Asia in 1997 and disrupted shipping and air travel, although the situation has improved over the weekend.

Hundreds of schools in the Malaysian districts have closed until further notice.

Singapore has sharply criticized Indonesia over the pollution, while Malaysia has avoided getting involved in the row. On Friday, Indonesian President Susilo Bambang Yudhoyono ordered a mobilization of "all the country's resources" to extinguish peat and land-clearance fires on Sumatra, which lies west of Singapore.

Yudhoyono's intervention followed a call from Singapore's environment minister, Vivian Balakrishnan, for Jakarta to take "definitive action" and a remark by Indonesia's coordination minister Agung Laksono that "Singapore shouldn't be like children, in such a tizzy."

jr/mkg (Reuters, AFP)