Schools were closed and masks distributed yesterday as air quality plunged in Malaysian Borneo after haze spread from forest fires in Indonesia.

Fourteen areas in Malaysia, including the capital, Putrajaya, and the largest city, Kuala Lumpur, recorded "unhealthy" air quality. Only three out of 51 monitoring stations recorded "healthy" air.

Flights have been cancelled and earlier this week a plane skidded off a runway in eastern Borneo because of poor visibility. "It's dark and gloomy outside," said Sri Laraswati, a hotel worker in the Indonesian city of Pontianak on Borneo. "Most people are wearing masks. People are coughing and staying inside. Visibility is a few hundred metres at best."

Hundreds of brush, forest and peat fires are burning in Sumatra and Borneo. Most are thought to have been started deliberately as a cheap and quick way to clear land, but experts say some, especially peat fires, could have started by themselves.

The late start to the rainy season is also playing a part. American officials warned yesterday that the developing El Niño weather pattern in the Pacific Ocean, which usually brings drier weather to south-east Asia, would linger into 2007.

Malaysia's environment minister, Azmi Khalid, told the Star newspaper that Indonesia was not doing enough about the haze. "I was in Jakarta in June and met the relevant ministers. They told me they had the systems to control the haze. It looks like their system is not effective."

Mr Azmi urged Jakarta to sign a regional agreement on the issue, but Indonesian officials claim they are working to stop the haze including cloud-seeding for rain.