Workers from Rosatom subsidiaries have installed the reactor internals and head, and have loaded dummy fuel assemblies in the reactor core, the statement said.
The company said that Rooppur-1, a VVER-1200 pressurised water reactor, is now ready to proceed towards cold hydraulic testing.
Cold hydraulic testing verifies that welds, joints, pipes and components in the primary circuit are able to withstand pressures higher than those during normal operation.
Russia is building two VVER-1200 pressurised water reactor units at the Rooppur site, about 150 km west of the capital Dhaka, under a general contract signed in 2015. Atomstroyexport, a Rosatom subsidiary, is the general contractor for the project.
The plants are the first commercial nuclear units to be bult in Bangladesh.
First concrete for Rooppur-1 was poured in November 2017 and for Rooppur-2 in July 2018.
Earlier reports had put target startup for Rooppur-1 in 2024, but the date will most likely be pushed back to late 2025.