A government official disputed the figures, saying they mischaracterized deforestation in the country.

Indonesia has one of the world's highest rates of deforestation, with key drivers including timber plantations, palm oil cultivation and, increasingly, the mining of critical minerals.

Its rainforests are some of the world's most biodiverse, providing crucial habitats for threatened and endangered species, and are key carbon sinks.

The report by NGO Auriga Nusantara said 261,575 hectares (646,366 acres) of primary and secondary forests across Indonesia were lost in 2024, over 4,000 more than the previous year.

The vast majority of the losses took place in areas opened for development by the government, the group added.

"It is worrying, as it shows the increase of legal deforestation," said Auriga Nusantara's chair Timer Manurung.

He called for "urgent" protection of forest in Kalimantan, where the highest losses were recorded as the country's new capital is built, and in Sulawesi.

Ade Tri Ajikusumah, a senior official at Indonesia's environment and forestry ministry, said the deforestation figure failed to account for replanting.

He acknowledged that government figures for "gross" deforestation in 2024 are "not significantly different" from Auriga Nusantara's, but that the NGO did not account for reforestation of over 40,000 hectares.

"We are now working to maximize land use," he said, adding that development around Indonesia's new capital involves "land that has already been released from forest status".

"These areas were previously managed by companies under existing permits. So it's not deforestation -- it was already designated for development."

The report comes as Indonesian environmentalists raise alarm over government plans to convert millions of hectares of forests for food and energy use.

President Prabowo Subianto, who assumed office in October, has pledged to boost food and energy self-sufficiency, including by expanding bio-based fuels to lower fuel imports.

Environmental groups warn the plans would spell disaster for the country's forests.

"We ask President Prabowo to issue a presidential regulation to protect all remaining natural forest," Timer told AFP.

The report is based on satellite imagery, which was analyzed to confirm deforestation, and followed up with field visits to areas representing tens of thousands of hectares of forest loss, Auriga Nusantara said.

While deforestation occurred in all of Indonesia's provinces except the region around Jakarta, the biggest losses were in Kalimantan.

One driver has been the designation of an area for the new capital, the report said.

Two regional governments in the area have proposed opening up hundreds of thousands of hectares of forest to potential development, the group warned.

Most deforestation however was driven by commodities, including timber, mining and palm oil.

Auriga Nusantara said its count excluded loss in timber plantations and plantation forest, but does cover both primary forests and regenerated "secondary" forest.

The report also sounds the alarm on deforestation for biomass production, which has seen forest levelled to plant quick-growing species that will provide wood biomass.

Indonesia is keen to boost domestic use of biomass energy and export, particularly to Japan and South Korea.

And it highlighted deforestation on islands in Raja Ampat, an area known for its teeming coral reefs, as nickel mining advances.

"This area of such national and international acclaim has been unable to withstand the onslaught," the report said.

Nearly 200 hectares across four islands in the region have been deforested, the group said, with new nickel mining licenses already issued for several more islands.

Auriga Nusantara said forest loss was also happening in conservation areas, despite legal protections.