Bangkok - Dense haze produced by Indonesian forest fires has caused some of the worst pollution levels in southern Thailand in a decade, officials said Thursday, delaying flights in an area popular with tourists.
For nearly two months, thousands of fires caused by slash-and-burn farming have suffocated vast expanses of Southeast Asia, causing rates of respiratory illnesses to soar, schools to close, and scores of flights and some international events to be cancelled.
Thailand usually avoids the worst effects of Indonesia's fires, which annually blight Malaysia and Singapore.
But in recent weeks prevailing winds have brought the smog further north, stoking tensions and creating a headache for the country's vital tourism industry.
Thai officials Thursday said air quality had dipped to unhealthy levels in seven southern provinces, with particularly high readings in southwestern Songkhla province where some flights have been delayed or turned back.
"It's considered a crisis. It's the worst in 10 years," Halem Jemarican, head of the Environment Office in Songkhla province, told AFP by phone.
"The key factor is the wind. It's strong at the hot spot origins but when it reaches Thailand the winds weaken so the haze stays around for longer," he added.
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An official at Songkhla's Hat Yai airport said three flights from Bangkok were delayed Thursday because of the haze while another flight from Bangkok to Hat Yai on Wednesday evening had to be diverted to Surat Thani.
Southern Thailand boasts many pristine tropical beaches and is an especially popular tourism destination.
Earlier this month several planes packed with beach-bound tourists to the resort island of Phuket and Koh Samui were forced to turn back because of haze levels.
Land is illegally cleared by burning in Indonesian tropical peatlands, which are rich in carbon but are being drained and cleared at a rapid rate to make way for agriculture, particularly fast-expanding palm oil plantations.
While the loudest complaints have come from leaders in relatively affluent Singapore and Kuala Lumpur, it is poor Indonesian villagers who are suffering most.
Many of those plantations are also owned by Malaysian and Singaporean companies.
Experts warn the current outbreak is on track to become the worst ever, exacerbated by bone-dry conditions caused by the El Nino weather phenomenon.
Indonesia earlier this month agreed to accept international help after failing for weeks to douse the fires and last week launched its biggest fire-fighting push yet, with dozens of planes backing up thousands of personnel on the ground.