The Russian-appointed military governor in Kherson, Volodymyr Saldo, said “all our Khersonite comrades want to receive the passport and [Russian] citizenship as soon as possible”.
Ukraine denounced the move as a “flagrant violation” of its territorial integrity, saying President Putin’s decree was “legally void”.
The policy follows Russia’s distribution of passports to residents of Ukrainian regions its forces have occupied since 2014 – Crimea and much of the Donbas.
Russia annexed Crimea and created self-styled “people’s republics” in Donetsk and Luhansk – moves condemned internationally.
Ukraine now fears the same process is under way in areas seized by Russian forces in the current invasion. Once locals become Russians, the Kremlin can claim it has to “protect” them.
There are reports of Ukrainians defying a Russian order to use roubles, instead of the Ukrainian currency hryvnia, in Kherson.
Melitopol is in the south-eastern Zaporizhzhia region, most of which is now held by Russian forces, including Europe’s biggest nuclear power station.
In Crimea and Russian-held Donbas – the industrial region made up of Donetsk and Luhansk – Russia has introduced the rouble and forced schools to adopt the Russian curriculum.
It has also ousted local officials appointed by Kyiv – and repeated such action in the newly-occupied areas.
Heavy fighting continues to rage in the Donbas city of Severodonetsk. The Kyiv-appointed head of Luhansk, Serhiy Haidai, says Ukrainian forces are still holding the city’s industrial zone, including the huge Azot chemical plant.