JOHANNESBURG (Reuters) - Thousands of South Africans burnt tyres and vehicles, barricaded streets and looted shops in the industrial town of Sasolburg near Johannesburg on Monday, the worst social unrest this year around the commercial hub of Africa's biggest economy.

Three police officers were injured when a mob threw stones at them in the town, 90 km (55 miles) south of Johannesburg, Constable Peter Kareli said.

In return, 50 officers fired rubber bullets and stun grenades and deployed water cannons to disperse the rioters, who went on the rampage because of a plan to move local government boundaries, he added.

"These people are attacking us in groups at different locations so it is difficult for us to control them," he said.

Some of the crowd were armed with knives, machetes and firearms and police had made at least 130 arrests since the violence broke out on Sunday, he added.

Sasolburg is home to the 108,000 barrels-per-day Natref refinery, owned by petrochemicals group Sasol and oil major Total. Kareli said the refinery was not in danger.

Violent protests erupt periodically in South Africa's predominantly black townships, which have seen little improvement in living standards since the end of apartheid in 1994.

(Reporting by Agnieszka Flak; Editing by Ed Cropley)

Due to the overwhelming enthusiasm of our readers it has become necessary to transfer our commenting system to a more scalable system in order handle the content.