Indonesian police have detained seven people whose companies are allegedly connected with illegal agricultural fires that have cloaked Southeast Asia in haze, in rare arrests over the annual smog outbreaks.
They were arrested on Wednesday on Indonesia's Sumatra island, where authorities have been battling smog-belching blazes which were started to clear land for palm oil and pulp and paper plantations, national police chief Badrodin Haiti said.

Police said some of those arrested were executives, but did not give details about all the company employees detained. Officials did not reveal their identities or say which firms they worked for.

They could face up to 15 years in jail and heavy fines if found guilty of breaking Indonesian laws that ban starting forest fires.

Tens of thousands have fallen ill in parts of Indonesia as the haze thickened over the past fortnight, and the smog has led to unhealthy air quality and reduced visibility in neighbouring Singapore and Malaysia.

"The president's instruction is clear -- law enforcement must be firm so that this will not happen again next year," Haiti told reporters late Wednesday, announcing the arrests.
President Joko Widodo pledged this week to crack down on companies and individuals behind the fires, and hundreds of extra police and investigators have been sent to haze-hit areas to hunt for those responsible.

They joined military personnel and water-bombing aircraft sent to tackle the fires.

In addition to the seven arrested, 133 people have been named suspects, Haiti said. This is a legal step in Indonesia that means investigators have enough evidence to consider filing charges against someone.

Indonesia has come under pressure from its neighbours to halt the smog outbreaks, an annual problem in Southeast Asia during the dry season.

The situation has been made worse this year by an El Nino weather system, which produces tinder-dry conditions in Indonesia and increases the risk of fires.

There were also fears that the haze could affect this weekend's glitzy Formula One night race in Singapore, but organisers have insisted the event will go ahead.