A US federal appeals court dismissed a lawsuit that alleged that five major tech companies were complicit in the use of child labour to mine cobalt in the Democratic Republic of Congo.

The lawsuit named Apple, Microsoft, Tesla, Dell Technologies and Google's parent company Alphabet.

The court ruled that the purchase of cobalt by the companies did not mean they participated in forced child labour on Tuesday.

Circuit Judge Neomi Rao also said that the plaintiffs failed to show that the accused companies had influence to stop the use of child labour in the mines.

"We are far from finished seeking accountability," Terry Collingsworth, a lawyer for the plaintiffs, told the Reuters news agency, adding that they might appeal against the ruling.

The case was first filed in 2019 by the human rights organisation International Rights Advocates, which was representing child workers who sustained injuries working in Congolese cobalt mines and the families of children who died in the mines.

It was dismissed by a lower court in 2021, prompting an appeal.

DR Congo produces 60% of the world's supply of cobalt, an essential mineral used in the manufacture of most electronic devices.

At least 25,000 children work on cobalt mines in DR Congo, according to the US Department of Labour, often in dangerous conditions.