Two killed at Lonmin S.Africa mine in union clash

* Union turf war is rocking S.African platinum sector

* Lonmin is world no. 3 producer of precious metal

* Its Western Platinum operation working at reduced capacity

* Latest flare-up signals rivalry is spreading

By Ed Stoddard

JOHANNESBURG, Aug 12 (Reuters) - Two security guards were hacked to death at a South African mine operated by the world's number three platinum producer Lonmin on Sunday in new violence between rival unions, company officials said.

Lonmin officials said the clashes were between the dominant National Union of Mineworkers (NUM) and the upstart Association of Mineworkers and Construction Union (AMCU). Their turf war for members shut the world's largest platinum mine run by Impala Platinum for 6 weeks earlier this year.

The latest flare-up began on Friday with an illegal strike by 3,000 rock drill operators at Lonmin's Western Platinum operations 100 kms (60 miles) northwest of Johannesburg, mirroring previous incidents when AMCU has sought to recruit NUM members.

In a number of clashes since, at least 6 workers trying to report for work were shot and wounded and the two security guards were killed on Sunday as a large group attempted to attack the company's facilities, Lonmin said in a statement.

Lonmin Executive Vice President Barnard Mokwena told Reuters the security guards had been hacked to death and the injured workers were NUM members.

"The police are on site and we have asked them to do a security assessment of the situation," he said.

He said the Western Platinum operation had not been shut but was working at reduced capacity because many of the workers were afraid to report for duty.

AMCU's National Treasurer Jimmy Gama told Reuters the union's leadership could not immediately comment on the situation as they needed to gather information from their local members.

Investors will take note that the AMCU/NUM rivalry, which has already caused friction at Lonmin's Karee mine, has now spread to other shafts.

Lonmin last month slashed spending plans up to 2014 as it warned that poor demand and weak prices battering the sector could persist for longer than expected.

The whole platinum sector is also grappling with the surge in union militancy. Aquarius Platinum earlier this month briefly shut one of its South African shafts after an attack that left three dead and at least 20 injured.

The stakes are high as South Africa sits on about 80 percent of the world's known platinum reserves.