The Democratic Republic of Congo is losing a fifth of all of mining revenues because of corruption and mismanagement, a campaign group has said.
In a report published on Friday, Global Witness said at least $750m paid by companies to the Congo's tax agencies and state-owned mining company Gecamines disappeared between 2013 and 2015.
At least some of the funds were distributed among corrupt networks linked to President Joseph Kabila, the group said.
The losses deprived the state of funds that should have been used on public services, it added.
Congo is Africa's top copper producer and the world's biggest supplier of cobalt, which is used in mobile phones and electric cars. It also produces coltan, diamonds, tin and gold.