Thousands of striking miners returned Wednesday to a mine where South African police opened fire on workers last month, killing 34 people.

An estimated 3,000 marchers, some carrying sticks, accused police of brutality at the Lonmin platinum mine, in the eastern town of Marikana.

Police in riot gear, armored vehicles and helicopters kept an eye on the demonstration.

The rally became tense at one point when some striking miners marched to the entrance of a shaft and threatened miners who were on the job. However, the protesters eventually dispersed peacefully.

Authorities fear strikes and unrest will spread to other mines. South Africa is a leading gold and platinum producer, and the mining sector is critical to South Africa's economy.

Separately, mediated talks resumed on Wednesday to settle the pay dispute between Lonmin and striking miners.

The workers' average monthly salary is currently about $480. They want their salaries tripled.

The strike is threatening to hurt Lonmin, the world's number-three platinum producer. The company says only 4 percent of miners showed up for work Wednesday.