Singapore (ANTARA News) - A grey haze from land and forest fires in Indonesian Sumatra enveloped Singapore on Monday, pushing the pollution index to its highest level this year, the National Environment Agency said.

"The smoke haze has also obscured the sunlight and lowered the temperature and visibility," the agency said in a statement.

At 0800 GMT the pollution index was at 73, in the moderate range but the highest recorded this year, the agency was quoted by AFP as saying.

"The latest satellite picture showed that there are 97 hotspots and dense smoke haze in Sumatra, mainly in Jambi and South Sumatra. The current dry weather conditions in southern parts of Sumatra are expected to persist until mid-October," the agency said.

Haze began to affect the affluent city-state on Sunday afternoon. Air quality also deteriorated Sunday along coastal areas of Malaysia's side of Borneo island, mainly because of open burning from Indonesia, officials in Malaysia said.

Indonesia's annual burn-off causes a haze that typically smothers parts of Malaysia, Singapore and Thailand as well as Indonesia itself.

The Indonesian government has outlawed land-clearing by fire but weak
enforcement means the ban is largely ignored.