Russia's ground forces on Thursday crossed into Ukraine from several directions, Ukraine's border guard service said, hours after President Vladimir Putin announced the launch of a major offensive.
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.
© Agence France-Presse