Russian President Vladimir Putin has signed papers formally declaring Russia’s annexation of four regions of Ukraine. Putin’s signatures came as Ukraine’s military continued to claim battlefield victories against Russia, saying it retook more settlements in Luhansk and Kherson — two of the regions claimed by the Kremlin.

Also on Wednesday, Putin signed a decree declaring Russian control over the Zaporizhzhia nuclear power plant, Europe’s largest nuclear station, which has been occupied by Russia’s military since March. In a video statement posted online, the head of Ukraine’s nuclear power agency called on employees at Zaporizhzhia to resist Russia’s bid to take over plant operations.

Petro Kotin: “I am sure that your bravery will not yield to your wisdom, and you will not sign any deals with the occupier, you won’t sign any statements and contracts. Don’t do it, under any circumstances. … We will continue to work under Ukrainian law with the Ukrainian energy system. Don’t doubt it.”