Vienna: The Secretary General of the OPEC oil cartel, Nigeria's Mohammed Barkindo, has died unexpectedly at the age of 63, the Nigerian National Petroleum Corporation said on Wednesday.

"We lost our esteemed Dr Muhammad Sanusi Barkindo. He died at about 11pm yesterday 5th July 2022," NNPC's chief executive Mele Kyari tweeted, without providing any further details about the circumstances of Barkindo's death, only a few hours after the head of the Organization of the Petroleum Exporting Countries had met the Nigerian president in Abuja.