Smoke rises from buildings in Kharkiv, Ukraine, on February 24, 2022.(Photo: Twitter)

Explosions were heard near major Ukrainian cities, including the capital Kiev.

Anton Gerashchenko, an adviser to Ukraine's Interior Minister, said on Facebook that the Russian military has launched missile strikes in Kiev, on military command facilities and the airport in Kharkiv, and along the border.  

NATO has denounced Russia’s attack against Ukraine, which it said puts countless civilian lives at risk.

The European Union Aviation Safety Agency has warned aircraft operators of a high risk to civilian aircraft over Ukraine.