Forest fires are raging once again on the Indonesian island of Sumatra.

Officials said satellite images show that the number of fires has rapidly increased in the last couple of days.

"On March 1, there were 90 hotspots and yesterday there were 296 hotspots mostly in the northern half of Sumatra," said Riadi Usman, an official from Riau province on the eastern coast of Sumatra.

Two years ago, forest fires on Indonesian islands caused an environmental catastrophe in Southeast Asia.

Blazing fires on Sumatra blanketed neighbouring Singapore and Malaysia with choking smog for months.

The current outbreak of fires is much less serious than in 1997 because the region is not so dry as before, and officials said the fires were unlikely to spread serious haze throughout the region.

"If the situation gets worse or spreads a little bit, we could get some slight incidence of haze" in Singapore, Meteorological Service spokesman Wong Teo Suan said.

The islands of Sumatra and Borneo have been repeatedly affected by forest fires. The blazes have hit hazardous levels affecting air traffic and public health for weeks.

Some of the fires are caused by lightning strikes, but many have been blamed on local farmers and forestry firms clearing land.

Despite a government ban on burning forests for land, the practice has continued unabated.

Indonesian authorities have blamed a lack of manpower, equipment, money and knowledge for their failure to control the fires.