Malaysia's health minister today warned of resentment against Indonesia and economic fallout as thick haze caused by Indonesian forest fires caused a sharp deterioration in air quality.

Malaysia also issued a hazard warning for ships plying the Malacca Straits after haze caused visibility to drop along the vital waterway.

Indonesia has been blamed for much of the haze from illegal land-clearing fires on Sumatra and the Indonesian portion of Borneo, and Health Minister Chua Soi Lek called on the country to step up its efforts to tackle the haze.

"We hope that the Indonesian government becomes more proactive in helping to solve this problem, because it not only causes resentment among our people, it also has economic implications," Chua told reporters.

"In terms of tourism, outdoor activities, even hawkers (street vendors) at night are affected," he said.

People don masks

Visibility was lowered in eastern Sarawak state as well as areas along Malaysia's west and south, while the Meterological Department said it would be less than five kilometres over the Malacca Straits until Thursday.

"This situation is hazardous to ships without navigational equipment," it said in a statement.

Figures from the Environment Department this morning showed air quality was at unhealthy levels in 14 areas in the country's west and south, including Kuala Lumpur and the administrative capital of Putrajaya.

In Kuala Lumpur, where the Air Pollutant Index was at an unhealthy reading of 159, people wore face masks on the streets to ward off sore throats and respiratory complaints.

Streets were largely empty in Putrajaya, which registered a reading of 171, as people complained of stinging eyes and hoarse throats.

A reading on the index between 101 to 200 is unhealthy, while 201 to 300 is very unhealthy.

Sign of frustration

In a sign of frustration with Jakarta, Chua said Indonesia was well aware of the consequences of the haze, which is an annual blight on the region.

"The Indonesian government is fully aware of the problem that they have created for all of us here in Asean, more so for Singapore and Malaysia, as immediate neighbours."

In Indonesia, light rains cleared one haze-choked region today but poor conditions persisted in other areas with air travel disrupted and residents forced to don face masks outside.

In Pekanbaru, the capital of Sumatra's Riau province, rains early today cleared the skies of the stifling smoke.

Singapore has also been hit badly by the fog-like haze this year, with authorities issuing a health advisory Saturday suggesting people should cut outdoor activity, although the situation there improved on Sunday.