Environmentalists, experts, and the government pointed the finger at deforestation for its role in last year's disaster that washed torrents of mud and wooden logs into villages across the northwestern part of the island.

The government is seeking 4.8 trillion rupiah ($283.8 million) from six companies accused of unspecified damage to an area spanning more than 2,500 hectares, the environment ministry said Thursday.

The sum represents both fines for damage and the proposed monetary value of recovery efforts.

The environment ministry declined to offer more details when speaking with AFP on the alleged damage caused by the defendants, listed in the statement only by their initials.

The suits were filed to courts Thursday in Jakarta and North Sumatra's Medan, the ministry added.

"We firmly uphold the principle of polluter pays," Environment Minister Hanif Faisol Nurofiq said in a statement.

Hanif warned in a statement Thursday that any corporation that "profits by damaging the ecosystem must be held fully responsible for restoring it".

Environmental groups say the government also holds some responsibility when granting companies the right to raze large tracts of land.

Greenpeace Indonesia's forest campaigner Arie Rompas called the lawsuits a "minimalist" move, adding that authorities should comprehensively review policies responsible for the disaster.

"Besides the impact of the climate crisis, the flooding was also caused by land degradation, including deforestation, carried out by corporations," Arie told AFP.

"Those companies were granted permits by the government."

Mining, plantations, and fires have caused the clearance of large tracts of lush Indonesian rainforest over recent decades.

Over 240,000 hectares of primary forest were lost in 2024, according to analysis by conservation start-up The TreeMap's "Nusantara Atlas" project.

Forestry Minister Raja Juli Antoni said last month that the government will revoke 22 forestry permits across the country, including permits that encompass more than 100,000 hectares in Sumatra.

Raja did not specify whether the decision was linked to the disaster, though earlier said that the floods provide an opportunity to "evaluate our policies."

The "pendulum between the economy and ecology seems to have swung too far towards the economy and needs to be pulled back to the centre," Raja said at the time.