Nigeria's state-owned oil company
has failed to pay the government $16bn (£11bn) in a suspected fraud,
according to an official audit.
The Nigerian National Petroleum Corporation (NNPC) provided no explanation for the missing funds, the auditor general told MPs.
Oil revenue accounts for two-thirds of the government's funding.
President Muhammadu Buhari has promised to crack down on corruption since coming to office last May.
