Thick haze from fires in Indonesia has caused the air quality over parts of Sarawak to hit unhealthy levels and visibility to plunge, officials said today.

In Sarawak's capital Kuching, the Air Pollutant Index hit 113 this morning, reaching into the unhealthy range of 101-200, a Department of Environment official told AFP .

In oil-rich Bintulu it recorded 105 and the towns of Samarahan and Sri Aman posted 117 and 119 respectively.

A Malaysian Meteorological Department official in Sarawak said the haze was due to fires in West Kalimantan, in the Indonesian part of Borneo.

"Normally it is caused by open burning in Kalimantan. We are in the monsoon period. The south-west winds brings the haze to Malaysia," the official told AFP on condition of anonymity.

Satellite images

The official said satellite images taken yesterday showed that there were 77 hot spots - or burning zones - in Indonesia's western Kalimantan and three in Sarawak's Miri.

The official said the haze has also caused visibility to dip below 6km in Kuching, Sri Aman and Bintulu - about half the normal level.

Burning in Indonesia and some parts of Malaysia to clear land for crops causes an annual haze that afflicts Malaysia, Singapore and Thailand as well as Indonesia itself.

The Indonesian forestry ministry last week denied that fires on Sumatra and Borneo were to blame for the latest haze smothering areas in Malaysia.

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