Five of the world's largest tech companies have been accused of being complicit in the death of children in the Democratic Republic of Congo forced to mine cobalt, a metal used to make telephones and computers, in a landmark lawsuit.

The legal complaint on behalf of 14 families from Congo was filed on Sunday by International Rights Advocates, a U.S.-based human rights non-profit, against Tesla Inc., Apple Inc., Alphabet Inc., Microsoft Corp. and Dell Technologies Inc.

The companies were part of a system of forced labor that the families claimed led to the death and serious injury of their children, it said.