A spate of wildcat miners' strikes spread to Africa's top iron ore producer on Wednesday, escalating the labour unrest that has become a major headache for South African President Jacob Zuma.The industrial action at Kumba Iron Ore, a unit of global miner Anglo American, further dented investor confidence in the continent's wealthiest economy as it showed the protests had moved beyond platinum and gold mines.Zuma is under fire for failing to address and contain the workers' protests, which stem in large part from glaring wealth inequalities persisting in South Africa since the end of apartheid in 1994.As many as 75,000 miners, or 15 percent of the South African mining sector's total workforce, are already out on strikes, while a national truckers' stoppage is squeezing fuel suppliers.Kumba, one of the world's top 10 iron ore producers, said the wildcat strike at its giant Sishen Mine in the Northern Cape involved only 300 employees and was limited to one area in the open cast mine, leaving most of the facility unaffected."The action is being dealt with in line with the Company's labour relations procedure, with due consideration to the safety of the vast majority of workers who are not taking part in the unprotected strike," Kumba said in a statement.Kumba's share price was over 4 percent lower on the news.The recent weeks of labour strife, in which around 50 people have been killed, have stirred up criticism of the ruling African National Congress and the presidency of Zuma, who faces a challenge from ANC rivals ahead of a party leadership conference in December. Agencies