More than 1,500 firefighters are battling scores of forest fires raging on Indonesian Borneo and Sumatra island as a haze envelops neighbouring Malaysia and Thailand, forestry officials said today.

Satellite images showed some 567 "hot spots" from fires and underground heat centres in Riau province on Sumatra as well as Kalimantan in Borneo, a spokesman from Indonesia's forestry ministry Masyud told AFP .

He said not all the spots were necessarily still burning as many would have been extinguished already.

Riau province on Sumatra island had the highest number of hot spots with 359, he said.

As many as 1,560 local firefighters were battling the fires armed with backpack water pumps, shovels and rakes, said Haryanto Wahyu Sukotyo, another forestry minister official.

He said most appeared to have been started to clear land in commercial timber or palm oil plantations.

"Most are in plantations, mostly it is palm oil, but we don't know for sure because we haven't investigated. But it is probably for land clearing," said Sukotyo.

Air quality unhealthy

Five provinces in Thailand, including the holiday isle of Phuket, have been hit by haze from the fires as has neighbouring Malaysia.

Air quality in the Thai province of Songkhla, 950km south of Bangkok, fell to potentially hazardous levels Tuesday morning, when visibility was reduced to two kilometers in the province.

In Malaysia parts of Penang, Perak, Selangor and Kedah were suffering poor visibility today from smoke particles being blown from Sumatra.

Yesterday, air quality in parts of Malaysia, including the major shipping centre of Port Klang west of the capital, plunged to unhealthy levels.

In May Indonesia's agriculture minister pledged to enforce a 2004 law. It imposes a maximum 10-year jail term and 10 billion rupiah (US$1.1 million) in fines on plantations that defy regulations against using fire to clear land.

Haze caused by burning in Indonesia and some parts of Malaysia to make way for crops causes an annual haze that afflicts countries in the region including Singapore and Thailand.

The worst-ever bout in 1997 and 1998 cost the region an estimated 9.0 billion dollars in damage by disrupting air travel and other business.