South African workers Monday hacked to death two police officers who came to quell deadly clashes between rival unions that claimed eight lives at a platinum mine run by leading producer Lonmin, police said.
"Our police officers were responding to a protest at the mine. They came under attack from the workers and two of them were hacked to death," said police spokesman Lindela Mashego.
A third officer is in critical condition in hospital following the unrest at Lonmin's Western Platinum mine about 100 kilometres (60 miles) from Johannesburg.
The firearms belonging to the officers were stolen.
Violent clashes broke out Sunday at the mine run by Lonmin, the world's third largest platinum producer, in a battle for dominance between the leading National Union of Mineworkers (NUM) and the smaller Association of Mineworkers and Construction Union (AMCU).
Eric Gcilitshana, NUM secretary for health and safety based at the mine, told AFP that one of the workers was founded hacked to death inside his house Sunday.
A second who tried to report for duty Sunday night was found dead with bullet wounds early Monday.
The London Stock Exchange-listed company confirmed in a statement on Sunday the murder of the two security guards, saying the incident followed an "illegal work stoppage and protest march on Friday" by some 3,000 rock drill workers.
The company said the strike action "quickly spiralled into criminal actions by rival factions."
In all, "ten workers were assaulted -- four were killed," said Gcilitshana before the death toll rose.
Police said later that four more workers died.
NUM has denied involvement in the killings and called for the army to be deployed to restore order.
"We appeal for the deployment of the Special Task Force or the South African Defence Force as a matter of urgency before things run out of hand," said NUM secretary general Frans Baleni said in a statement.
"Our members have been attacked and that cannot be said to be clashes or rivalry, it is pure criminality," he added.
According to the police, the workers were armed with "sticks and sharp objects."
The situation remains tense at the mine and several cars had been torched.
Deadly clashes at South African mines often occur during strikes over wages, when workers belonging to rival union do not heed to strike action.
In February two workers were killed at a platinum mine owned by Impala Platinum during a lengthy strike which shut down operations.
The mining sector is the biggest private employer in South Africa, which has one of the world's most unionised workforce.