STARVANGER: The world must continue to extract oil and gas in order to sustain civilisation, while also developing sustainable sources of energy, Tesla founder Elon Musk told reporters at a conference in Norway on Monday.

"Realistically I think we need to use oil and gas in the short term, because otherwise civilisation will crumble," Musk said on the sidelines of an energy conference in the southern city of Stavanger.

Asked if Norway should continue to drill for oil and gas, Musk said: "I think some additional exploration is warranted at this time."

"One of the biggest challenges the world has ever faced is the transition to sustainable energy and to a sustainable economy," he said. "That will take some decades to complete."

He said offshore wind power generation in the North Sea, combined with stationary battery packs, could become a key source of energy. "It could provide a strong, sustainable energy source in winter," he said.

He also voiced concerns over birth rates, echoing remarks he made in a Twitter post late last week on the risks of "population collapse".

"One of my less obvious things to be concerned about is the birth rate, and I think its important that people have enough babies to support civilisation so that we don't dwindle away," Musk said.