More than 30 people were killed when South African police officers opened fire on striking workers at a Lonmin PLC mine, the Police minsistry has confirmed.

Spokesman Zweli Mnisi gave the figure on Friday after Thursday's shooting in Marikana, just northwest of Johannesburg.

He said an investigation into the shooting had begun.

The protest and ensuing violence at the platinum mine, which began a week ago, has killed at least ten people there, including two police officers.

It has also drastically affected production at the mine.