Russia’s defence ministry said on Thursday that its air attacks on Ukraine were not targeting cities and posed no threat to civilians, the RIA news agency reported.
Ukraine said earlier that at least eight people had been killed and nine were wounded by Russian shelling.
Russian tanks and other heavy equipment crossed the frontier in several northern regions, as well as from the Kremlin-annexed peninsula of Crimea in the south, the agency said.
It said one of its servicemen died in a shelling attack along the Crimean border, the first officially confirmed military death of the Russian invasion.
Ukraine has suffered heavy casualties in its eight-year conflict with Russian-backed rebels in the separatist east, but has reported no fatalities along its southern border with Crimea for some years.
Early on Thursday, Kyiv said at least five Russian aircraft and one helicopter were shot down.
“On Feb. 24, 5 aircraft and an aggressor helicopter were shot down near the area of the Joint Forces,” Ukraine’s Command of Joint Forces said on Facebook.
“The Joint Forces give a worthy rebuff to the armed forces of the Russian Federation,” said the statement.
Noting that Ukraine’s military units are keeping their positions, the command said “the enemy suffers losses”.
“Keep calm and believe in Ukrainian defenders. Let’s win together!” it concluded.
Meanwhile, Russia’s defence ministry denied its aircraft or armoured vehicles had been destroyed in Ukraine. The ministry said it had neutralised Ukrainian military airbases and its air defence systems.
“Military infrastructure at Ukrainian army air bases has been rendered out of action,” the defence ministry said in a statement carried by news agencies, which added that Kyiv’s air defence systems were “eliminated”.