Nearly 500 miners have locked themselves in a coal mine near Turkey's capital in a show of protest against a privatisation project, a union representative told AFP on Friday.

The protest started on Wednesday against a plan to privatise the Cayirhan mine and thermal power plant on the outskirts of Ankara.

"Around 500 miners have locked themselves in the mine. Their colleagues and family members are also here to support them," Talih Kocabiyik of Turkey's Maden Is union told AFP.

"The miners are worried about the future, about their job security and their working conditions," Kocabiyik said.

The incident in Soma in western Turkey where 301 miners were killed in 2014 after an explosion and fire caused a shaft to collapse, still remains etched in memories.

The leader of the main opposition CHP party, Ozgur Ozel, and Ankara mayor Mansur Yavas also from the CHP visited the miners on Thursday to show support.

"After privatisations, there will be layoffs, pressure on production and concerns about safety at work," Ozel said during the visit.

"That is why we oppose this privatisation," he added.

According to Kocabiyik, the miners are determined to continue their protest until the privisation project is abandoned and if not they are planning to start a hunger strike.