Russia claimed on Sunday that its troops had reached the border of Ukraine's Dnipropetrovsk region, as tensions escalated between Moscow and Kyiv over stalled peace talks and the repatriation of thousands of war dead.

Amid talk of peace, the war is stepping up with Russian forces grabbing more territory in Ukraine and Kyiv unfurling high-profile drone and sabotage attacks on Russia's nuclear-capable bomber fleet and, according to Moscow, on railways.

Russia, which controls a little under one-fifth of Ukrainian territory, has taken more than 190 square kilometers (73 square miles) of the Sumy region of eastern Ukraine in less than a month, according to pro-Ukrainian open-source maps.

Now, according to the Russian Defense Ministry, units of the 90th Tank Division of the Central Grouping of Russian forces have reached the western frontier of Ukraine's Donetsk region and are attacking the adjacent Dnipropetrovsk region.

"The enemy does not abandon its intentions to enter the Dnipropetrovsk region," Ukraine's Southern Defense Forces said on Telegram.