South African environmental activists declared a major victory Wednesday after winning the country's first climate change case and forcing the government to reassess the impact of a coal power plant.

The group, Earthlife Africa, successfully challenged a government decision to confirm construction of a proposed coal-fired power station, arguing that the proper climate change impact assessment had not been carried out.

Environment minister Edna Molewa accepted that the impact of the proposed Thabametsi power plant had not been "comprehensively assessed or considered" -- but granted environmental approval anyway, according to the ruling seen by AFP.

North Gauteng High Court judge John Murphy ordered that the environment ministry must now complete a climate change assessment before construction of the plant, due to be built in northern Limpopo province, can proceed.

Earthlife Africa spokeswoman Makoma Lekalakala told AFP that the ruling sent "a very strong message to government and to locals to take part in consultation before any decision takes place."

"It is a landmark ruling that actually holds the department of the environment to account," she added.