Penang was hit today by haze caused by fires on Indonesia's Sumatra island, a meteorological official said.

A senior official with the Meteorological Department, Donis Gunting, said the haze, carried by southwesterly winds, moved to mainland Penang state and its tourist island overnight on Tuesday.

"At the moment visibility is more than 10 kilometres, which is considered normal, but this morning it was bad," Donis told AFP .

At the height of the haze at 9am, he said visibility in Penang was reduced to 800 metres.

Indonesia's Sumatra island is to Malaysia's west, and Donis said officials had identified 177 hotspots from fires there.

Seven hotspots in Pahang

He said peninsular Malaysia currently had seven hotspots in the south of Pahang, and seven in East Malaysia's Borneo island, but that the haze in Penang had been caused by Sumatra hotspots.

"It was caused by the fires on Sumatra because the wind is south to southwesterly," he said, adding the haze was brought by the annual southwest monsoon.

"This period is the southwest monsoon, so with the hotspots in Sumatra, it will definitely come again. It will depend on the prevailing wind directions," he said.

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

The worst-ever bout, in 1997 and 1998, cost the region an estimated US$9 billion by disrupting air travel and other business activities.

Indonesia earlier this year vowed to crack down on palm oil plantations that contributed to the problem by burning land, while Malaysia has said it will name and shame plantations which conduct burning.