Ukrainian officials on Saturday accused Russia of planning a fake referendum on creating a pro-Moscow "people's republic" in the southern Black Sea city of Kherson.
Russian forces seized the port city, which has a population of 290,000 people, on March 3 following a three-day siege. It was the first major city to fall following Moscow's invasion.
"Russians now desperately try to organize a sham 'referendum' for a fake 'people's republic' in Kherson," Foreign Minister Dmytro Kuleba tweeted.
Due to "zero popular support," such a referendum "will be fully staged," he added.
"Severe sanctions against Russia must follow if they proceed. Kherson is & will always be Ukraine," the minister added.
Kuleba drew a parallel with Russia's annexation of the Black Sea peninsula of Crimea in 2014, when it held a referendum on joining Russia after deploying troops there.
The Kherson plan was following a "2014 playbook," Kuleba said.
Ukraine's ombudsman Lyudmyla Denisova wrote on Telegram that Russian occupying forces were phoning lawmakers from the local legislature, asking them to vote for the plan.
Denisova said such a referendum would be illegal on the occupied territory, since under Ukrainian law any issues over territory can only be resolved by a nationwide referendum.