About  2,000 stick-wielding workers at South Africa’s violence-hit Marikana mines are marching to gain support for their wage strike.It is the biggest demonstration at Marikana since police shot dead 34 miners last month, sparking outrage. The protesters, closely watched by police, are advancing to a Lonmin-owned mine to get non-striking workers to join the strike. About 50 miners controversially charged with the murders were freed on Monday.About another 220 miners still in police custody are expected to be released on Thursday. The BBC’s Karen Allen in Marikana says police helicopters circled overhead as the protesters, holding long sticks, marched through Marikana town in North West province.The protest is taking place as church leaders continued mediating between Lonmin and worker representatives in an effort to negotiate a peace accord. Lonmin, the world’s third biggest platinum producer, said worker attendance at its Marikana mines was less than 5%."We expect that employees are waiting for the outcome of the peace accord meeting,” it said in a statement. A man at the head of the demonstration waved a placard which said, "We want 12,500 rand ($1,480; £935) - nothing else”. A protester told Reuters news agency that they were heading to Lonmin’s Karee mine to "take out the people who are working in the mine shaft”.Rock-drill operators embarked on a strike about a month ago, demanding higher wages and greater recognition for a new union, the Association of Mineworkers and Construction Union (Amcu), which is a rival to the long-established National Union of Mineworkers (Num).The striking workers accuse Num of being too close to Lonmin, and failing to press their wage demand in talks with management. Former Num General-Secretary Cyril Ramaphosa is a Lonmin director. The miners, who say they are currently earning between 4,000 and 5,000 rand a month, want their salary increased to 12,500 rand.