A Ukrainian presidential aide said on Monday a demilitarised zone of 100-120 km (62-75 miles) should be established inside Russia along the border with Ukraine as part of a post-war settlement.
The zone would be necessary to protect Ukrainian regions from shelling, presidential adviser Mykhailo Podolyak wrote on Twitter.
"The key theme of the post-war settlement should be the establishment of safeguards to avoid the recurrence of aggression in the future," he wrote.
To ensure the safety of residents in several frontline Ukrainian regions, he wrote, "it will be necessary to introduce a demilitarization zone of 100-120 km on the territory of Belgorod, Bryansk, Kursk, and Rostov republics."
The reference to the Russian regions as republics appeared to be a nod towards Moscow backing separatist entities calling themselves "people's republics" in Ukraine's Donetsk and Luhansk regions which border Russia.
Podolyak said the demilitarised zone could initially have an interntional presence to control it.
"Probably, at the initial stage with a mandatory international control contingent," he wrote.
