KUALA LUMPUR (REUTERS) - Malaysia has sent half a million face masks to its eastern state of Sarawak, where air pollution levels have spiked amid worsening forest fires in neighbouring Indonesia, authorities said on Tuesday (Sept 10).

Indonesian farmers often use fire to clear land for palm oil and pulp plantations. Fires can smoulder for weeks, especially in dry weather, producing a choking haze that drifts over neighbours like Singapore and Malaysia.

In recent weeks, Indonesia has sent in thousands of security personnel to douse fires after declaring an emergency in six provinces on the islands of Sumatra and Borneo.

"Nadma has acquired 500,000 face masks and sent them to the agency's branch in Sarawak," Malaysia's national disaster management agency said in a statement, referring to itself by it acronym.

The agency and the education ministry were also working to get masks to schools in the affected area, it said.

The air pollution index (API) in Sarawak, on the Malaysian side of Borneo, reached unhealthy levels on Tuesday with one district recording a reading of 201, a "very unhealthy" level.

Unhealthy readings were recorded in five other Malaysian states.

South-east Asia has suffered for years from annual bouts of smoke caused by slash-and-burn practices in Indonesia, raising worries about health and the impact on tourism. Indonesia's neighbours have repeatedly complained and promised to help end the problem but it persists.

Indonesia last week said it had detected haze crossing over from Kalimantan in Borneo to the Malaysian side on the island.

But on Tuesday, its climate agency disputed findings by Malaysia and Singapore that the countries were also seeing smog from fires on Sumatra island.

"As for transboundary haze, there has been none detected from the area of Sumatra towards the Malaysian peninsula," the climate agency said. It added that signs of forest fires were also spotted in Malaysia, the Philippines, Papua New Guinea, Vietnam, East Timor and Thailand.

Singapore recorded slightly hazy conditions on Tuesday due to persistent fires in Sumatra's Riau and Jambi provinces, the country's national environment agency said.

"Given the air quality forecast for the next 24 hours, healthy persons should reduce prolonged or strenuous outdoor physical exertion," the agency said.

"Persons who are not feeling well, especially the elderly and children, and those with chronic heart or lung conditions, should seek medical attention," it added.

Last week, Malaysia said it would send a diplomatic note to Indonesia urging immediate action to fight the haze.

Malaysia has also offered Indonesia help to put out the fires, but had yet to receive any request for assistance, the disaster agency said.