(Adds comment by CEO, number of injured)
JOHANNESBURG, Oct 4 (Reuters) - Work at South African miner Sibanye Gold's Cooke mine has been suspended after two members of the National Union of Mineworkers were left in a critical condition after being attacked, a spokesman for the company said on Tuesday.
In total four Sibanye employees suffered injuries in the attacks, which were related to an illegal strike that started on Monday following a dispute about union membership verification, the firm said in a statement.
In the first half of 2016 the three working shafts at Cooke produced around 100,000 ounces of gold, about 13.5 percent of the group's total gold production.
Sibanye's share price was down 2.7 percent at 46.52 rand by 1130 GMT, making it the biggest decliner in Johannesburg's Top-40 index.
"We cannot have the mines operating when we cannot guarantee the safety of our workers. No one went underground last night and no shifts began this morning," company spokesman James Wellsted said.
NUM spokesman Livhuwani Mammburu said the miners were attacked by members of the rival Association of Mineworkers and Construction Union. AMCU officials could not immediately be reached for comment.
The incident is the latest flare-up between the unions, which have been locked in a turf war which has killed dozens of moneworkers since AMCU dislodged NUM as the dominant union in South Africa's platinum belt in 2012.
"We are in discussions with AMCU to resolve their concerns," Sibanye Chief Executive Neal Froneman said, adding that the firm was investigating the incidents and would take action against the perpetrators. (Reporting by Ed Stoddard and TJ Strydom; Editing by Louise Heavens, Greg Mahlich)