Foreign minister K. Shanmugam met his counterparts from Indonesia and Malaysia in Bandar Seri Begawan on Saturday to discuss the problem of the haze caused by forest fires in Sumatra.
The three ministers are in Brunei for a series of annual meetings of the Association of Southeast Asian Nations.
The haze has been severe this year, with air quality in Singapore and parts of Malaysia at unhealthy or hazardous levels for days.
Mr Shanmugam, Mr Marty Natalegawa of Indonesia and Anifah Aman of Malaysia held talks behind closed doors soon after they arrived for the ASEAN meetings, which began on Sunday, AFP reported from Bandar Seri Begawan.
Meanwhile, Prime Minister Lee Hsien Loong said the number of hotspots in Sumatra had fallen steadily over the last few days.
"This is good news! I hope the situation continues to improve over the next few weeks," he wrote on his Facebook page.
The National Environment Agency (NEA) said the Pollutant Standards Index is expected to be in the moderate range of 51-100 during the 24 hours ending at 6pm on Sunday.
But it said "the health advisory for this period corresponds to the unhealthy band".
This was because the 24-hour PM2.5 level, which indicates the fine particles in the air, was expected to be slightly elevated.
Those with chronic illnesses should avoid all outdoor activity and wear N95 masks if they cannot avoid it, NEA said in its daily haze forecast.
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