The air quality in Malaysia worsened today and visibility at airports nationwide remained poor due to smog from forest fires in neighbouring Indonesia.

The number of areas in west peninsula posting unhealthy pollution levels rose to nine from seven on Monday, the environment department said.

In Malacca, which faces Indonesia's Sumatra island, readings on the Air Pollutant Index registered 121. Readings in the range of 101-200 on the index are deemed unhealthy.

Also badly hit were the towns of Johor Bahru, Muar and Larkin in southern Johor state, which neighbours Singapore, with readings of 134, 121 and 126 respectively.

In Kuala Lumpur, the pollution index rose slightly today to near unhealthy level of 98, higher than Monday's 80.

Air travel unaffected

Visibility at Kuala Lumpur International Airport was down to three kilometres, less than half the normal 10km. But officials said poor visibility had not affected air travel.

Indonesian farmers burn forests annually to clear land for agriculture, causing a smokey haze that spreads around the region during the dry season, affecting tourism and causing health problems.

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

Environment ministers from Singapore, Malaysia and other regional nations have urged Indonesia to promptly ratify a regional treaty aimed at preventing cross-border haze pollution.