The likelihood of transboundary haze hitting Singapore is low so far as the prevailing wind is from the north-east, the National Environment Agency (NEA) said in an advisory on Tuesday night. But Singapore may experience occasional slight haze due to accumulation of particulate matter under stable atmospheric conditions, it added.

A sharp rise in burning hotspots was detected on Tuesday, as haze in the Sumatran city of Dumai once again soared to very hazardous levels.

There were 458 hot spots detected by satellites, up from the 187 detected on Monday. The fires across Sumatra are set to clear land for farming, and have been exacerbated by the current dry weather.

In a Facebook post on Tuesday night, Environment and Water Resources Minister Vivian Balakrishnan wrote: "We will try to encourage them to take action - but we all know the welfare of close neighbours is not their priority.

"Hard truths of regional politics."

Last week, NEA chief executive Ronnie Tay and Singapore consul for Indonesia in Medan Mark Low met with Fachrori Umar, deputy governor for Sumatra's Jambi province, to discuss handling the haze, reported the Jakarta Post.

In June last year, Singapore experienced its worst-ever bout of haze, with the PSI hitting a record high of 401 at one point.

Air quality updates are available from www.nea.gov.sg, www.haze.gov.sg, on www.facebook.com/NEASingapore or on Twitter @NEAsg.