SINGAPORE (AP) -- Air pollution in Singapore soared to record heights for a third consecutive day, as Indonesia dispatched planes and helicopters Friday to battle raging fires blamed for hazardous levels of smoky haze in three countries.
The blazes in peat swamp forests on Indonesia's Sumatra island have sent massive plumes of smog across the sea to neighboring Singapore and Malaysia, both of which have grown impatient with Indonesia's response to the perennial problem.
Singapore is suffering its worst haze in history. Its main air pollution index hit a measurement of 401 at midday Friday, exceeding previous highs of 371 on Thursday and 321 on Wednesday, both of which were record readings. Those measurements were classified as "hazardous" and can aggravate respiratory ailments.
The index, which has fluctuated widely this week, eased to as low as 139 by Friday evening, still in an unhealthy range.
Singapore's environment minister, Vivian Balakrishnan, flew to Jakarta on Friday to discuss measures to tackle the forest fires that break out in Indonesia during midyear dry spells because of carelessly discarded cigarettes and illegal blazes set by plantations and farmers to clear land.
"People, to be honest with you, are angry," Balakrishnan told reporters in Indonesia. "People want to see action on the ground."
Balakrishnan's Indonesian counterpart, Balthasar Kambuaya, pledged that Jakarta will investigate and take stern legal action against those who started fires. Some Indonesian officials have suggested that Malaysian and Singaporean companies might be among those responsible.
Sutopo Purwo Nugroho, an official in Indonesia's National Disaster Management Agency, said 10 aircraft were sent to Sumatra on Friday to help extinguish the fires. Three helicopters will lead a "water-bombing" effort to assist more than 100 firefighters on the ground, while planes will conduct "cloud-seeding" to try to chemically induce rain.
The dirty, acrid haze has slashed visibility and shrouded many of Singapore's towering landmarks, forcing airports to take extra precautions, the military to reduce outdoor training and some fast food businesses to suspend delivery services. Elderly residents, children and pregnant women have been advised to avoid all outdoor activity.
Plagued by the stifling smell of burning vegetation that crept even into homes and offices in this wealthy city-state, residents flocked to pharmacies to buy protective face masks after Singapore's Prime Minister Lee Hsien Loong urged people to remain indoors as much as possible.
"I don't know if it's just my imagination but even indoors, my throat is starting to feel weird," said business manager Tan Joa-Quim. "I want a mask but my company has a limited supply, which we prioritized for the older and less healthy staff, and a lot of shops have sold out."
Some airports in Sumatra have closed because of poor visibility and pollution levels that exceeded Singapore's.
In neighboring Malaysia, officials shut nearly 600 schools Friday in southern districts near Singapore. Most of Malaysia, including the main city, Kuala Lumpur, was not as badly affected, though two southernmost towns recorded hazardous air quality.
Malaysia's environment minister plans to travel to Indonesia next week to discuss the problem.
Associated Press writers Sean Yoong in Kuala Lumpur, Malaysia, and Ali Kotarumalos in Jakarta, Indonesia, contributed to this report.