The activist group Greenpeace has dumped five tons of coal outside the headquarters of South Africa's power utility to protest construction of a new power station.

Three trucks dropped off the coal outside an entrance to Eskom's Megawatt Park in Johannesburg Monday.

The environmental activists are demanding the state-owned company stop building the coal-fired Kusile power plant.

Greenpeace spokeswoman Melita Steele said Eskom should instead focus on developing renewable energy and energy efficiency.

An Eskom official accepted a letter from Greenpeace listing the reasons for the protest.

About 90 percent of South Africa's electricity is produced by coal-powered plants. The country endured widespread blackouts in 2008, prompting Eskom to try to increase capacity.