The air quality in Malaysia worsened on Tuesday and visibility at airports nation-wide remained poor due to smog from forest fires in neighbouring Indonesia, officials said.
The number of areas in west peninsula posting unhealthy pollution levels rose to nine from seven on Monday, the environment department said.
In the historical state of 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 the capital, Kuala Lumpur, the pollution index rose slightly Tuesday to 96, higher than Monday's 80.
Visibility at Kuala Lumpur International Airport was down to three kilometres (1.86 miles), less than half the normal 10 kilometres. 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.