By Peter Apps

SECUNDA, South Africa (Reuters) - A South African mayor dismissed rioting by thousands of protesters complaining of poor public services as political opportunism, saying on Wednesday great strides had been made in service delivery.

Protesters smashed windows and tried to torch municipal buildings in Secunda on Tuesday, angered by a government decision to cut off electricity and water to those who cannot afford to pay the bills.

They also say poor sanitation threatens their health and security by forcing many to use buckets as toilets and take the raw sewage out at 2 a.m. to be picked up by truck.

"Sometimes the truck is not there. Sometimes the sewage is spilled all over," Buhle Mlambo told Reuters at her house in a shanty town in eMbalenhle township, 12 km (7.456 miles) from Secunda.

Being out so early put the women at risk of being raped, she added.

Riots over poor service delivery have sporadically broken out in towns in South Africa's Free State, but the Secunda riots mark the first time they have been seen in Mpumalanga province. Most have been in areas with high unemployment, where many still live in shacks despite government re-housing efforts.

Around Secunda, which is about 100 km (60 miles) from Johannesburg, many people are employed in a plant owned by synthetic fuel giant Sasol.

LOCAL ELECTIONS

More than a decade after the end of apartheid, analysts say the violence could threaten the ruling African National Congress in local elections later this year.

The riots, which the mayor said involved about 4,000 people but organisers say included as many as 40,000, began after eMbalenhle residents marched to Secunda council offices after municipal Mayor Mdibanisi Tsheke did not appear to address a residents' meeting earlier in the morning.

Tsheke said he did not know residents were expecting him, and said the march was illegal.

"In my opinion I think it's just a ploy so the organisers make sure that they position themselves for local government elections," he told Reuters in the offices where marchers broke several windows after reaching the town.

"Some of them want to stand for election afterwards."

Tsheke said he noted great strides in service delivery.

Many more people had access to water, electricity and sanitation than in the past, he said, and by June the 5,000 households using "informal sanitation" would have access to proper sewage.

March organiser Oupa Mvundla said he would not comment on whether any of the organisers had political ambitions, but said the issues were local and not related to Free State riots.

"We are not fighting the ANC. We love the ANC," said Mvundla, who sits on the committee that organised the protests though he denied any involvement in the violence.

"We are fighting the local element of the ANC which is trying to enrich themselves," he said.

But some analysts disagree and say the phenomenon is beginning to worry the ANC.

"To some extent, there does seem to be a degree of imitation," said Tom Lodge, lecturer in political science at Johannesburg's University of the Witwatersrand.

"It's very important at the moment because they have local government elections at the end of the year and you're going to see some successful small parties to the left of the ANC," he said.