SINGAPORE - Hazy conditions over Singapore are expected to persist for the next one to two days, the National Environment Agency (NEA) said on Thursday.

As of 4pm, the 24-hr PSI was between 80 and 90, in the moderate range.

However, the air quality is expected to move into the low end of the unhealthy range in the early evening.

The latest satellite image showed persisting widespread moderate to dense smoke haze in central and southern Sumatra, which has spread to Singapore.

For the next few days, the hotspot and haze situations are not likely to change significantly under the dry weather conditions, unless wind speeds pick up.

Conditions could even deteriorate further if prevailing winds shift to blow from the south or southwest.

NEA chief executive officer Ronnie Tay wrote to his Indonesian counterpart on Tuesday to register Singapore's concerns over the situation.

He has also reiterated the Republic's offer to help combat the haze problem.

The Asean Specialised Meteorological Centre (ASMC), which has a regional warning system for fire and haze situations, said that Sumatra has met the conditions for Alert Level 3.

This occurs when there are 250 or more hotspots detected on two consecutive days with dry weather conditions persisting and prevailing winds blowing towards other Asean countries.

A total of 395 hotspots were detected in Sumatra on Wednesday.

Given the air quality forecast for the next 24 hours, healthy people should reduce prolonged or strenuous outdoor physical exertion while the elderly, pregnant women and children should minimise these activities.

Those with chronic lung or heart disease are advised to avoid prolonged or strenuous outdoor physical exertion and those who are not feeling well should seek medical attention.

Members of the public are advised to refer to the Ministry of Health's advisory and NEA's daily haze situation update before participating in outdoor activities.

The NEA said it will continue to monitor the situation closely and issue updates as the need arises.