The situation was so worrying that up to 2,059 people in Chiang Mai and 1,000 people in Chiang Rai were seeking treatment at local hospitals every day - most of them with coughs, sore throats and eye irritation. The number of patients in other affected provinces was also on the rise.

"It is estimated that up to 500,000 people may suffer health problems from the haze. We need to provide swift and comprehensive services," Deputy Public Health Minister Morakot Kornkasem said.

The thick haze now covers Chiang Mai, Chiang Rai, Lampang, Phrae, Nan, Lamphun, Mae Hong Son and Phayao.

Public Health Ministry permanent secretary Dr Prat Boonya-wongvirot said the war room was operating from a provincial public-health management office and officials would work until 8pm every day.

"Officials will analyse the situation on a daily basis and plan solutions accordingly. The war room will closely coordinate with local public health authorities in the eight affected provinces," he said.

Meanwhile, a Thai military unit sent an urgent letter to the Thai-Burma Township Border Committee (TBC) asking for help in reducing fires on the Burmese side.

"We understand that Burmese people have to burn some areas of forest to prepare land for farming, but we would like to request they ensure their activities are as limited as possible," Colonel Suthas Jarumanee said.

He said if the Burmese authorities agreed to help, the haze problem over Chiang Rai would be reduced by half.

In Chiang Rai, public health officials were handing out 12,000 masks to local people to help them cope with the pollution.

"But given the scope of the problem, we believe we will need up to 120,000 masks," Chiang Rai public health chief Dr Thepnarumit Methanawin said.

He said the situation was particularly serious in Mae Chan and Phan districts where the number of patients with respiratory symptoms had increased sharply.

In Chiang Mai, the haze problem had lessened slightly but the amount of dust particles remained threateningly high.

In Mae Hong Son, up to 107,643 families were suffering from problems resulting from the smoke and haze. Yesterday, 3,000 masks were handed out.

"We now have officials ready around the clock to extinguish forest fires," Thepnarumit said. Since January, 99 forest fires have raged through 950 rai of forestland in Mae Hong Son.

In Lampang, more than 200 patients had sought treatment for respiratory symptoms from a local hospital this month.

"The number of patients looks set to increase," Lampang Governor Amorntat Nirattisayakul said.

In Lamphun, local officials handed 13,000 masks to local people.

In January, the number of patients at seven state hospitals rose sevenfold compared with the same period last year.

Deputy Prime Minister Paiboon Wattanasiritham, who also serves as Social Development and Human Security Minister, yesterday convened a meeting of all 13 relevant authorities to tackle the haze problem in the North.

The meeting lasted more than two hours.

"We have to reduce fire spots, especially on the plains," Paiboon said.

According to Paiboon, the Interior Ministry promised to coordinate with relevant authorities to ensure that no more fires would be burning on the plains within three days.

"Within seven days, fires in the entire area should be reduced from more than 800 spots to just 250," Paiboon added.

Today he will visit Chiang Mai to survey areas being declared "disaster-hit" zones.