Moving away from civilian nuclear power was a "strategic mistake," for Europe, according to European Commission chief Ursula von der Leyen, who argued on Tuesday that the Middle East war had exposed the continent's fossil fuel "vulnerability."

"It was a strategic mistake for Europe to turn its back on a reliable, affordable source of low-emission power," she said at the opening of a nuclear energy summit just outside Paris as the U.S.-Israeli war with Iran entered its second week.

"For fossil fuels, we are completely dependent on expensive and volatile imports. They are putting us at a structural disadvantage to other regions," she said at the summit, which aims to boost the use of civilian nuclear energy.

"The current Middle East crisis gives a stark reminder of the vulnerability it creates," she added.

"We have home-grown low-carbon energy sources: nuclear and renewables. And together, they can become the joint guarantors of independence, security of supply, and competitiveness – if we get it right."

French President Emmanuel Macron struck a similar note, saying civilian nuclear power helped provide energy sovereignty.

"Nuclear power is key to reconciling both independence – and thus energy sovereignty – with decarbonization, and thus carbon neutrality," Macron said at the second Nuclear Energy Summit.

"We can see it in our current geopolitical context: when we are too dependent on hydrocarbons, they can become a tool of pressure, or even of destabilization," he added.

Von der Leyen said that "while in 1990, one-third of Europe's electricity came from nuclear, today it's only close to 15%."

She announced that the European Union would "create a 200-million-euro ($230-million) guarantee to support investment in innovative nuclear technologies."

Nuclear energy fell into crisis after the 2011 Fukushima disaster in Japan, which reinforced fears highlighted by the 1986 Chornobyl catastrophe.

But the growing international focus on energy sovereignty and the search for clean energies to counter global warming has reignited atomic interest.

Nuclear power accounts for about 9% of electricity produced in the world, with some 440 reactors in around 30 countries, according to the World Nuclear Association.