Russian president Vladimir Putin has announced a partial military mobilisation in Russia that starts Wednesday.
In a televised address to the nation, he said this was a necessary step to ensure Russian territorial integrity.
He said the West wanted to destroy Russia.
Russia’s defence minister said in an interview that 300,000 people could be called up.
Meanwhile, Western nations have condemned Moscow’s plans to hold urgent so-called referendums in parts of Ukraine that are currently under Russian control.
Administrations in Luhansk, Donetsk, Kherson and Zaporizhzhia say they will begin this Friday.
The US, Germany and France have said they would never recognise the results of such “sham” ballots.
US President Joe Biden and Ukraine’s President Zelensky will address world leaders later at the United Nations General Assembly.