Moscow: Russian President Vladimir Putin on Wednesday announced the imposition of martial law in four areas of Ukraine that Russia announced it had annexed last month.

The four regions occupied by Russian are Donetsk, Luhansk, Kherson and Zaporizhzhia. Putin made these comments during a security council meeting, CNN reported.

"In this regard, let me remind you that in the Donetsk People's Republic, the Luhansk People's Republic, as well as in the Kherson and Zaporizhzhia regions, martial law was in effect before joining Russia," Putin said during a televised address.

"Now we need to formalize this regime within the framework of Russian legislation," he said, adding that a decree of martial law in these four regions of the Russian Federation has been introduced formally and will be immediately sent to the Federation Council, CNN reported.

Earlier on Wednesday, the Russian leaders in the annexed regions started relocating people in huge numbers amid global condemnation.

After Russia annexed four Ukrainian regions of Donetsk, Luhansk, Kherson and Zaporizhia, concerns have sparked globally that Moscow could resort to nuclear weapons.

Putin formally announced the annexation of four regions - Donetsk, Luhansk, Kherson and Zaporizhia recently and claimed that "this is the will of millions of people," according to CNN.

Putin said the residents in the four annexed regions will now be Russia's "citizens forever".

Russia's annexation has sparked wide criticism from around the world. The United States announced that it will impose a "swift and severe cost" on Russia.

Meanwhile, US Secretary of State Antony Blinken said that the "United States unequivocally rejects Russia's fraudulent attempt to change Ukraine's internationally recognized borders."

After Putin's formal announcement of the annexation of the said four regions, western leaders condemned it, termed it "illegal" and vowed that they will "never recognize" these areas.