Indonesia has faced global pressure to put an end to slash-and-burn clearance of land, often to plant palm and pulp plantations, particularly after devastating fires in 2015.

Farmers use fire to clear land during the dry season can rage out of control, bringing a choking haze that can affect neighbors such as Singapore and Malaysia.

Drought has hit large parts of the archipelago as a mild El Nino weather pattern disrupts the dry season, weather officials say, with its peak now expected to run from mid-August to mid-September.

"The number of hot spots has been increasing, with 124 intense enough to suggest fires detected nationwide by Wednesday morning," said Agus Wibowo, a spokesman for the National Disaster Mitigation Agency.

The government has declared an emergency in the provinces of Riau, South Sumatra, West Kalimantan, Jambi, South Kalimantan and Central Kalimantan, where extensive peatlands are particularly prone to fires, he added.

Authorities have brought in 5,679 additional personnel to five of the provinces, drawn from the military, police and the regional disaster mitigation agency, Wibowo said.

Also being deployed are aircraft that can run water bombing operations. In Riau, disaster authorities have made available 17 helicopters, with 10 more pressed in from private firms, the military and the forestry ministry, he added.

In Riau's capital of Pekanbaru, some teachers and school children wore masks in classrooms and were urged to limit outdoor activity because of haze concerns, the Antara state news agency said.

To help stop the fires and preserve crops, authorities are turning to cloud-seeding, by shooting salt flares into clouds to try and trigger rains.

Nearly 50 million of Indonesia's population of 260 million face drought in 28 of its 34 provinces, said Dody Usodo Hargo Suseno, an official of the coordinating ministry for human development.

President Joko "Jokowi" Widodo, who is on a trip to the island of Sumatra, called officials from the military chief on down to urge them to immediately stop the forest fires, the cabinet secretariat said in a statement.

This month, the Supreme Court upheld a judgment against Jokowi, cabinet ministers and provincial governors that attributed blame over their handling of the 2015 fires.

REUTERS