More than 400 fires have been recorded burning in Indonesia's Riau province of Sumatra so far in June, a huge increase from the same time last year, officials said Tuesday.

Riau province is located across the Straits of Malacca facing Johor in Malaysia.

klia haze aircraft landing 161006 Smoke from the fires is causing haze that is drifting across Malaysia, where authorities said on Friday air quality and visibility in some areas had fallen from "good" to "moderate" over the previous week.

Most of the illegal fires were the result of land and forest clearing for traditional farming and palm oil plantations, forestry ministry official Israr Albar said.

"The number of hotspots may increase two to three-fold this month. The farmers are clearing land for cultivation in more areas," he said.

"Land cleared by local residents accounted for 65 to 70 percent of the fires."

Start of the dry season

There were 401 hotspots in Riau this month compared to 227 in the whole of June last year, he said.

Almost 1,000 hotspots were detected in Riau, 73 in West Kalimantan and 18 in Central Kalimantan last month, the start of the dry season.

Agricultural burning during the dry season, which ends around September, is an annual source of smoky haze that affects tourism and contributes to health problems across the region.

The government has outlawed land-clearing by fire but weak enforcement means the ban is largely ignored.

Environment ministers from Singapore, Malaysia and other regional nations have urged Indonesia to promptly ratify a regional treaty aimed at preventing cross-border haze pollution.

Nine hotspots in Sumatra today

riau province hot spots dated 16 june 160609 However, according to satellite images , Riau currently has only nine hotspots.

Experts nevertheless expect more forest burning in the coming three months.

As of 11am today, the Environment Department's Air Pollution Index showed 13 out of 49 areas nationwide, or 26 percent, with 'moderate' readings.

Miri in Sarawak has the highest reading of 71, followed by Pasir Gudang in Johor Baru.

Readings of between 0 and 50 shows good air quality while 51 to 100 is moderate. Those above is considered 'unhealthy'.

Last Friday, three areas in Malaysia registered unhealthy API readings - Port Klang (138), Shah Alam (120) and Cheras (107).

But air quality was better in subsequent days.

- AFP