JOHANNESBURG, Gauteng (AFP) - Over 160,000 South African workers will be on strike this week when petrol attendants and car repair workers join ongoing stoppages in the construction sector, and more gold miners grumble.

Mass industrial action has pummelled Africa's largest economy since August, with tens of thousands of gold , construction and car manufacturing employees demanding higher pay and stalling production in sectors that represent 10 per cent of the gross domestic product (GDP).

Now, 73,000 workers at fuel stations and garages will down tools from Monday after talks with employers collapsed, according to the National Union of Metalworkers of South Africa (Numsa).

They will kick off the strike with marches in Cape Town and Johannesburg, which will spread to other cities later in the week and could severely affect transport and business.

"We want to settle on double digits. We want basically to improve the conditions of workers," Numsa general secretary Irvin Jim told AFP.

Fuel attendants earn around 700 rands (S$89) a week, according to the union, who represents a third of the sector's workforce.

Meanwhile around 90,000 construction labourers have refused to work for 12 days, according to their labour group the National Union of Mineworkers (NUM).

"The strike is still continuing," NUM negotiator Bhekani Ngcobo told AFP.

The builders earn 4,000 rand basic salary and want it pushed up by 800 rand, the union said after lowering an earlier demand. Employers are offering 400 rand, according to Ngcobo.

Some other sectors have gradually restarted production.

A wage deal at South Africa's third gold producer Harmony Gold ended a short-lived mass strike that had crippled an industry that contributes three per cent to GDP.

"Members of the NUM have accepted the same offer made by other producers in the industry, and have returned to work," Harmony Gold said in a statement on Sunday.

Tens of thousands of miners had downed tools for four days demanding salary hikes of up to 60 per cent, during which the gold sector stood to lose US$34 million (S$43.4 million) in production every day.

By Friday strikers at most of the Chamber of Mines' seven members had accepted a new wage offer of up to 8.0 per cent. The final holdouts, Harmony Gold employees, agreed to the deal Sunday, the firm said.

"The majority have accepted the offer," NUM general secretary Frans Baleni told Sapa news agency.

But rival union the Association of Mineworkers and Construction Union (AMCU) rejected an 8.0-per cent increase offer and mooted industrial action in the gold sector.

"That is for NUM, that is not for AMCU," said national organiser Dumisani Nkalitshana amid fierce competition between the two labour groups.

AMCU represents just under 20,000 - or a fifth - of affected gold workers. On Sunday these "voted for a strike. But they said we must approach the Chamber of Mines to come on board and negotiate," Nkalitshana told AFP.

If new talks with producers broke down, the union would give 48-hour notice to strike, according to AMCU president Joseph Mathunjwa.

They are demanding 12,500 rands, almost double their basic salary, an amount that echoes a rallying call in violent platinum sector stoppages last year.

AMCU's bitter fight for supremacy with the government-allied NUM fired up what employers considered inflated and unrealistic wage demands. It has already displaced NUM in the platinum sector and is making inroads at gold mines too.

Harmony chief executive Graham Briggs warned the gold sector could not maintain similar wage hikes as Sunday's deal, which was "in the interests of long term industrial relations stability".

Falling gold prices, a declining grade of ore and increased costs such as electricity and wages, have drained profits, and many firms are now looking to cut costs.

Meanwhile car manufacturing was also set to return to normal after a three-week stoppage.

Most of the 30,000 strikers were happy with the industry's new offer: 11.5 per cent increase this year, and 10 per cent annually until 2015, according to Numsa, who said talks continued with workers from the BMW factory in Pretoria and the Toyota plant in eastern port city Durban.

This year, strikes have been relatively calm in contrast to those of 2012, when a police crackdown at Lonmin's Marikana platinum mine left 34 dead and sparked deadly labour unrest all over the country.