KUALA LUMPUR • Malaysia may have to pass a law forcing its companies to tackle fires on land they control abroad, Malaysian Prime Minister Mahathir Mohamad said yesterday, as forest fires in neighbouring Indonesia spread haze across the region.

South-east Asia has suffered for years during the dry season from bouts of smoke caused by fires - many in Indonesia - that are set to clear land, raising worries about health and the impact on tourism.

The smoke, or haze, has been particularly bad in recent weeks, leading to accusations and angry responses among the neighbours.

Indonesia's Environment Minister Siti Nurbaya Bakar told Reuters last week that some of the fires in her country had been spotted on oil palm plantations operated by at least four subsidiaries of Malay-sian companies.

Tun Dr Mahathir said his government would call on the Malaysian companies to put out the fires.

"But, of course, if we find that they are unwilling to take action, we may have to pass a law which will make them responsible for fires on their property, even if they are outside Malaysia," Dr Mahathir told reporters.

Veteran Malaysian politician Anwar Ibrahim said in an interview with Bloomberg Television yesterday that the haze constituted ecological warfare.

"We should feel outraged, and I consider this an ecological warfare," said Datuk Seri Anwar.

"It is not a small matter. It is affecting essentially millions of our people," he said, noting this requires governments to be more assertive.

"We have to be stronger, regardless of whether it is Malaysia, Singapore or Indonesia - I mean these are big companies. Why are we not making sure they are being held accountable and at least bear part of the cost?"

Illegal fires to clear land for agriculture are blazing out of control on Sumatra and Borneo islands, with Jakarta deploying thousands of security forces and water-bombing aircraft to tackle them. The Indonesian blazes are an annual problem, but this year's are the worst since 2015.

Thousands of schools across Indonesia and Malaysia were closed yesterday as air pollution in the region worsened.

Air quality deteriorated to "very unhealthy" levels yesterday on an official index in many parts of Peninsular Malaysia, to the east of Sumatra, with the Kuala Lumpur skyline shrouded by dense haze.

Nearly 1,500 schools were closed across Malaysia due to the air pollution, with more than one million students affected, according to the Education Ministry. The two worst-affected states were Selangor, where 538 schools were closed, and Sarawak, with 337 closures. Hundreds of schools in other states such as Perak and Penang were also affected.

A growing number of Malaysians were experiencing health problems due to the haze, with the authorities saying there had been a sharp increase in the number of outpatients at government hospitals, and that many were suffering from dry and itchy eyes.

The Indonesian authorities said hundreds of schools in hard-hit Riau province on Sumatra were shut, while about 1,300 were closed in Central Kalimantan province on Borneo.

The Indonesian government has insisted it is doing all it can to fight the fires, with President Joko Widodo saying during a visit to Sumatra on Tuesday that "we have made every effort".

This year's fires have been worsened by dry weather, and experts believe there is little chance of them being extinguished until the onset of the rainy season next month. Indonesia's meteorology, climate and geophysics agency said yesterday that over 1,000 hot spots had been sighted, most of them on Sumatra.

The haze is also affecting endangered orang utans on Borneo, with dozens of the young apes at rescue centres contracting respiratory infections, according to the Borneo Orangutan Survival Foundation.

REUTERS, BLOOMBERG, AGENCE FRANCE-PRESSE