By Ed Stoddard
JOHANNESBURG (Reuters) - A senior union official was shot dead outside an Impala Platinum (Implats) mine on Tuesday in South Africa's Rustenburg area, the focus of a surge of violence that has unnerved investors.
The branch treasurer with the powerful Association of Mineworkers and Construction Union (AMCU) was "gunned down in cold blood" as he left the mine, 100 km (60 miles) west of Johannesburg, to get food, his organisation said in a statement.
It did not give details on any motives for the attack, which was confirmed by Implats. Police were not immediately available for comment.
Labour and social strife in South Africa's platinum belt, the source of more than 70 percent of known reserves of the precious metal, has piled pressure on an industry already hit by depressed prices.
Rustenburg has seen periodic spasms of labour violence including shootings since AMCU dislodged the once dominant National Union of Mineworkers (NUM) as the main union in the sector five years ago.
AMCU president Joseph Mathunjwa told Reuters there had been other attacks in the Rustenburg area.
"A month ago a branch leader at Lonmin (LON:LMI) had an attempt on his life as well," Mathunjwa said. Another AMCU member at Lonmin, who had been dismissed but was appealing the decision, was shot dead shortly after, he added.
Mathunjwa said he would not speculate on the motives behind the incidents.
Lonmin spokeswoman Wendy Tlou confirmed that an AMCU member at the mine had recently been shot and was now recovering out of hospital while another who was no longer an employee had been shot and killed.
In August 2012, police shot dead 34 AMCU members during a violent wildcat strike at Lonmin's Marikana operation, the bloodiest security incident in the post-apartheid era.