The Nuclear Safety and Security Commission approved permits to build the Shin Hanul 3 and 4 reactors after it "confirmed the safety" of the project in southeast Uljin city.

"No factors have been found at the reactor construction site that could cause geological disasters such as subsidence or ground collapse," it said.

Each reactor will have a capacity of 1.4 gigawatts, and they are scheduled to be built by 2033.

Seoul sought to phase out nuclear energy under the leadership of Moon Jae-in, whose government aimed to make South Korea completely nuclear-free by 2084.

But since Yoon Suk Yeol took office in 2022, his government has ambitions to increase the share of power generated from nuclear energy to 36 percent by 2038, up from the current 30 percent.

The new reactors will "contribute to the development of cutting-edge technologies such as AI by providing a stable supply of clean and reliable energy," said Sung Tae-yoon, Yoon's chief of staff for policy.

The development could also "help the country secure reactor construction bids overseas", he told reporters.

The approval came eight years after Korea Hydro & Nuclear Power Company first submitted the permit request. The process was suspended in 2017 amid the then-government's push to reduce the country's dependence on nuclear energy.

Thursday's decision was criticised by Korean activist group Energy Justice Actions as an "irresponsible move that threatens the safety of the people, in opposition to the global trend towards an energy shift" towards renewable resources.

The two new reactors will be Uljin's ninth and tenth, the group said, calling such a concentration a "global rarity".