Police used a water cannon and stun grenades to disperse rioters in South Africa's strike-hit platinum belt on Sunday after a government minister was attacked by rock-throwing protesters while campaigning for the May 7 elections.

The riot is the latest in a series of strikes for higher pay that has claimed dozens of victims since 2012, when police shot and killed more than 30 workers in the Marikana massacre. The incident further undermined the ruling African National Congress' commitment to supporting the country's working class, and strife has continued as a union opposed to the ANC gains power.

A union rivalry — between the striking Association of Mineworkers and Construction Union (AMCU) and the group from which it split, the National Union of Mineworkers (NUM), a key ANC ally — adds fuel to an already combustible social and political mix in the area, which has been hard hit by the strike.

Police spokesman Thulani Ngubane told Reuters that a community hall, municipal center and the house of a councilor for the ANC were burned down. He would not identify the rioters, but local media and union leaders said the minister was attacked by members of the AMCU.

Ngubane confirmed that Sports Minister Fikile Mbalula had to be whisked away under police protection after he and other campaigning ANC supporters were confronted by a crowd in the shantytown of Freedom Park, northwest of Johannesburg.

It was after this that the protest erupted into a full-scale riot, Ngubane said.

Sydwell Dokolwana, the regional secretary for the NUM, a close ally of the ruling party, told Reuters that he was with the minister at the time and that several people were hurt in the scuffle.

"There was a group of about 100 guys with AMCU shirts. We had to run for our lives," he told Reuters. "They said they would only allow us to campaign if the ANC assisted them in getting $1,200," he said.

The AMCU's battle cry has become "12,500 rand" ($1,200), which is the minimum monthly wage it is seeking from the world's top platinum producers, Anglo American Platinum, Impala Platinum and Lonmin.

While it has backed down from an initial demand that that wage — more than twice the current one — be granted immediately, its 70,000 members remain off the job after talks to end the 13-week-old strike collapsed last week.

Employers have taken their latest offer directly to the workers, betting that AMCU members have lost their will to strike after going three months without pay. Some workers said they were going hungry after weeks of inaction.

Striking miner Jeffery Shipulale told Reuters that at this point, he is ready to accept almost any offer from his employer, Lonmin.

"We will even accept 1,000 rand [$94]. We are hungry. There is no money," the Mozambican national said as he and his wife hawked tomatoes, onions and loose cigarettes at a stand in the mining town of Marikana, where police killed more than 30 workers at the height of a 2012 labor strike.

AMCU officials could not be immediately reached for comment on the outbreak of violence.

Households and local businesses are struggling as the miners have collectively lost almost $660 million in wages, according to an industry website that constantly updates the tally.

The AMCU emerged as the top union in the platinum shafts after poaching tens of thousands of NUM members in a vicious turf war in 2012 that culminated in the Marikana massacre and triggered a wave of violent wildcat strikes that year.

South Africa on Sunday marked two decades of multiracial democracy, 10 days before elections that are expected to keep the ANC in power.

The flare-up on the platinum belt reflects the huge tensions in the "rainbow nation," which has glaring income disparities and often violent labor unrest.

Al Jazeera and Reuters