ABUJA (Nigeria) — Nigerian authorities have announced Wednesday that the Secretary-General of Organization of Petroleum Exporting Countries had died.

Mohammad Barkindo (63), died Tuesday night, a spokesperson for Nigeria’s petroleum ministry said to The Associated Press. His cause of death was not immediately clear.

Mele Kyari (Managing Director, Nigerian National Petroleum Company Limited) tweeted about Barkindo’s passing. He described it as “a great loss for his immediate family, NNPC and our country Nigeria, OPEC, and the global energy community.”

Barkindo, a Nigerian national, has led the crude oil bloc from August 2016 and saw it through some of its most turbulent periods, including the pandemic, when oil prices were declining.

When he died, he was finishing up his tenure with OPEC. Barkindo was the former leader of the Nigerian Petroleum Corporation and Deputy Managing Direct of Nigerian Liquefied Natural Gas. This joint venture between NNPC, Shell, Total, and Eni is a joint venture between NNPC, multinational oil giants Shell and Eni.