A wildfire on Khao Chaphlu in Nakhon Nayok's Muang district on Tuesday evening was moving closer to residential areas yesterday after having burned 700 rai of forest across three mountains.

Authorities fear strong winds in the area may cause the fire to spread towards Khao Yai National Park, which is just three kilometres away.

The Meteorological Department, meanwhile, warned that if this fire isn't contained within the next three to four days, Bangkok and its surrounding provinces will get severe air pollution.

Nakhon Ratchasima, Buri Ram, and Prachin Buri have been seriously affected by the smoke.

Authorities expect to completely contain the fire in about five days, though all efforts were being made to ensure the operation wraps up in about three days.

The Department of Disaster Prevention and Mitigation has sent three helicopters to help fight the blaze, a source said.

A team of firefighters from Khao Yai National Park began moving on foot towards the fire zone yesterday as the fire appeared to slow down, said the head of Khao Yai National Park.

However, he said the blaze might spread rapidly again if wind speeds increase.

The fire, which began on Khao Chaphlu and was reportedly caused by a lightning strike, spread to Khao Laem and Khao Tabaek overnight on Tuesday and Wednesday.

As of press time yesterday, the fire on Khao Chaphlu and Khao Tabaek was still visible, while the fire on Khao Laem was believed to have been brought under control.