JOHANNESBURG: Lawyers for South African mineworkers charged with the murder of colleagues shot by police said on Friday they believed their detention to be unlawful and called on President Jacob Zuma to free them.

In an open letter to Zuma, the lawyers asked him to take all necessary steps to secure the release of the 270 mineworkers by 1100 GMT on Sunday, "failing which an urgent court application will be launched in the High Court to compel you to do so".

"It is our view that the arrests of our clients were and remain unlawful," said the letter.

"Their continued detention is also unlawful".

The workers have been held in custody since their arrest on August 16 when police shot 34 miners and wounded 78 near the Lonmin platinum mine in Marikana, northwest of Johannesburg.

On Thursday the workers were charged under a common purpose rule for the murder of the 34.