INDONESIA on Wednesday urged airports in areas shrouded by thick smoke from forest fires to close if conditions made landings' hazardous, after a jet with more than 100 on board skidded off a runway in Borneo.

The passenger jet operated by Mandala Airlines skidded off the runway upon landing amid thick haze in Indonesia's East Kalimantan province on Tuesday as fires spread choking haze to neighbouring Singapore and Malaysia.

``We recommend that authorities determine minimal visibility standards in airports. If visibility is below the standards, an airport should be closed temporarily,'' said Setyo Raharjo, the chairman of the National Commission for Transport Safety.

The current regulations allowed a pilot to decide whether it was safe enough to land, he told Reuters.

Raharjo said haze had contributed to the mishap involving one of Mandala's Boeing 737-200 aircraft. No one was hurt after the jetliner skidded 50 metres (164 ft) off the runway in Tarakan.

An air traffic controller at Cilik Riwut airport in Central Kalimantan said there had been some landing delays on Wednesday.

``In the morning it is usually dark (with visibility) around 400 metres. It usually lasts until 2 pm (0700 GMT) when visibility rises to between 800 metres to 1 km,'' said Zamroni who, like many Indonesians, is known by one name.

The haze, caused mostly by farmers and plantation owners setting fires to clear land, has forced many flights to be delayed or cancelled in Indonesia in recent days.

South-southwesterly winds have blown smoke from fires in central and south Sumatra to Singapore and Malaysia, obscuring sunlight and reducing temperatures and visibility. The haze appeared to worsen in Malaysia on Wednesday, with pollution levels rising to unhealthy levels in more areas.

The Borneo state of Sarawak next to Kalimantan remained the worst-affected area and has been blanketed by smog for weeks. ``Today is the worst so far,'' one resident in the Sarawak state capital Kuching said by telephone.

``Schools remain open but many people are already wearing face masks.''

At the daily 0300 GMT reading, the air-pollution index (API) showed ``unhealthy'' levels in most areas in Sarawak. Malaysia's capital Kuala Lumpur was also covered by haze with the API level rising to just below the ``unhealthy'' mark.

Visibility at the capital's main airport fell to 3,000-4,000 metres from the usual 10,000 metres, an airport official said.

Singapore's Pollutants Standards Index (PSI) hit the highest level this year on Monday, although fell back a day later.

Masud, an Indonesian forestry ministry spokesman, said most fires were in plantations and criticised local governments for not doing enough to stamp out land-clearing by burning.