Update | Malaysian PM Najib urges Indonesia to act on smoke-belching fires as haze creeps further north into Thailand

Malaysian Prime Minister Najib Razak has called on Indonesia to take action against people setting fires that have caused choking smoke to drift across the region, with the sky over southern Thailand the latest to be clouded by the pollution.

Indonesia has come under pressure in the past few weeks to contain the annual haze crisis, which is caused by slash-and-burn agriculture on Sumatra island and its part of Borneo island.

Companies seeking to clear land for palm oil and pulp wood plantations have been accused of encouraging the fires that often smoulder for weeks in underground peat deposits.

The problem has been exacerbated this year by the El Nino weather phenomenon which has brought unusually dry conditions.

"If this is done by people or by farming companies, Indonesia needs to take decisive action against the perpetrators," Najib said on Twitter late on Sunday.

Schools in Malaysia and Singapore have closed when the smoke has been heavy, sports events have been cancelled and tourism operators are fretting. Health authorities across the region warn people to avoid exercise on bad days.