Greenpeace activists climbed parts of a coal-fired power station under construction east of Johannesburg and planned to spend the night there to protest what they call South Africa's unnecessary dependence on coal, the environmental group said Monday.

Greenpeace spokeswoman Fiona Musana said the protest started early Monday with activists locking the gates of the construction site. She added that six activists then climbed pillars at the site where they plan to spend the night.

“Construction of this place should stop now,” Musana said.

Coal electricity plants are the main source of greenhouse gas emissions by South Africa, which hosts climate change talks later this year. Greenpeace said South Africa should be moving faster away from coal and invest heavily in solar and wind power.

Eskom, the state-owned electricity company, says it needs Kusile, expected to be completed in 2016, and Medupi, a coal plant scheduled for completion in 2015, because of rising electricity demand. Eskom also has renewable projects planned.

Last month, the World Bank approved $250 million in funding for to help Eskom build solar power and wind power plants. Last year, the World Bank approved a $3.75-billion loan to Eskom for the Medupi coal power station. - Sapa-AP