The Russian parliament’s upper chamber has voted overwhelmingly to revoke President Vladimir Putin’s right to order military intervention in Ukraine.
The decision is effective immediately.
Ukraine is struggling to stamp out a rebellion by pro-Russian separatists in the east of the country.
Kyiv has agreed a limited ceasefire to give rebels time to lay down their weapons or leave the country.
But the rebel attacks have not stopped and Ukrainian President Petro Poreshenko has threatened to end the truce.
The ceasefire is supposed to last until Friday, when Kyiv plans to sign a free trade agreement with the European Union.
EU leaders may then consider further sanctions against Russia over its role in Ukraine.