Workers have lifted into place the fourth tier of the internal steel containment building shell at the Akkuyu-2 nuclear power station in Turkey, Russian state-owned nuclear power corporation Rosatom said.
Rosatom said the component weighs about 140 tonnes and is eight metres high.
The next stage of construction will include the welding together of the third and fourth tiers.
The containment building shell will consist of 12 tiers when complete and will subsequently be covered in concrete and tested for hermetic tightness.