South Africa's fourth ranked gold producer, DRDGOLD , said on Friday some 3,300 workers at its Blyvoor gold mine had launched an illegal strike during Thursday's night shift.

DRDGOLD said in a statement it had obtained an interim court order against the workers, which ordered the workers to cease the illegal strike and return to work at the mine near Carletonville, in the north west province.

It was unclear how the strike would affect mine production.

James Duncan, a spokesman for DRDGOLD said he did not know the total number of workers at the Blyvoor mine, but said the 3,300 workers on strike were a majority of the mine's workforce.

He said they were still on strike on Friday, and it was not yet clear when they would heed the court order to resume work.

The mine normally operates on Saturdays and has a night shift on Sunday, Duncan said.

Shares in DRDGOLD, a relatively junior gold producer with all its operations in South Africa at three different mines, fell 0.98 percent to 6.08 rand after it released the statement, while the gold mining sector index rose 0.4 percent.

The company said the workers on strike were mostly semi-skilled. Their action was sparked by the arrest of two DRDGOLD employees by police in connection with the death of one man and the assault of another -- neither of whom were DRDGOLD staff -- in December 2007.

In the first quarter to end-March, total gold production at Blyvoor fell 6 percent to 32,343 ounces, mainly owing to the impact of power cuts that affected mine operations, after state utility Eskom [ESCJ.UL] struggled to meet power demand.

DRDGOLD has faced two consecutive weeks of disruption to its operations after workers at its struggling ERPM mine stayed away from work last week following days of attacks targeted at foreign nationals, in which two of DRDGOLD's staff died.

ERPM said earlier this week normal attendance had resumed, after scared Mozambican, Lesotho and Swaziland nationals who are employees at the mine returned to work after the violence ebbed.

Migrant workers are accused by many poor South Africans of taking scarce jobs and fuelling violent crime.

DRDGOLD said lost output at the mine to the east of Johannesburg would be quantified at the end of the current quarter, which runs to end-June. (Reporting by James Macharia, Editing by Peter Blackburn)

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