BAMAKO (Reuters) - Rioters in southern Mali ransacked local government buildings on Monday following a dispute between workers and management at Randgold’s Loulo and Gounkoto gold mines, the government said.

The rioters attacked the local prefect’s office and house and also burned biometric voter identification cards that were to be used in next month’s presidential election, according to a statement by the ministry of territorial administration.

A spokeswoman for Randgold, which owns three gold mines in Mali, did not immediately respond to a request for comment.

It was not immediately clear what the dispute was about. Workers went on strike at Loulo and Gounkoto in April over bonus payments but the standoff was resolved within a day.

The Loulo and Gounkoto mines are located in Mali’s gold-rich south, far from the unrest caused by Islamist insurgents in the north. They produced more than 20 tonnes of gold last year.

Mali is Africa’s third-largest gold producer, behind South Africa and Ghana.