OPEC Chief Mohammad Barkindo told an energy conference in Nigeria's capital, Abuja, that "We could unlock resources and strengthen capacity if the oil produced by the Islamic Republic of Iran and Venezuela were allowed to return to the market."

Both nations are under strong sanctions for sponsorship of terrorism and other acts.

"Our industry is now facing huge challenges along multiple fronts," he told conference delegates.

"And these threaten our investment potential now and in the long term. To put it bluntly, my dear friends, the oil and gas industry is under siege," he said, citing geopolitical developments in Europe, where the war in Ukraine has left many countries vulnerable to soaring energy prices.

Strain on the industry has been increased by some countries' efforts to divest from hydrocarbons, Barkindo stated.

While they are seeking to limit global warming, he said oil demand was growing even as investment in capacity falls and prices surge.

Nigeria's oil minister Timipre Sylva said Africa's top oil producer would not abandon fossil fuels.

"For us in Nigeria, fossil fuel will always have a share in our energy mix, for the foreseeable future. We will not at this time abandon fossil fuels. We have adopted ... gas as a transition fuel," he said.

Barkindo forecast primary demand for oil globally would increase up to 2045, while refining capacity in the Organization for Economic Cooperation and Development countries fell by 3.3% in 2021.