European Union chief Ursula von der Leyen on Wednesday floated the idea of a "specialized court" to put Russia's top officials on trial over the war in Ukraine.

On the ground, Russia said it had captured a few settlements in eastern Ukraine, eager for a win after a series of setbacks since invading its pro-Western neighbor in late February.

"While continuing to support the International Criminal Court, we are proposing to set up a specialized court backed by the United Nations to investigate and prosecute Russia's crime of aggression," she said.

The main problem is that the International Criminal Court (ICC) does not have jurisdiction over Russia's "crimes of aggression" — its invasion and war in Ukraine — because Moscow is not a signatory to the court's treaty.

Von der Leyen is instead proposing to have a court set up in an EU country that could tackle Russia specifically on the crime of aggression, while leaving war crimes and crimes against humanity to the ICC.