Russia launched an overnight air strike on Kyiv, with the city's air defense forces trying to repel the attack, the military administration and the mayor of the Ukrainian capital said on Sunday.
"Explosions in the capital. Air defenses are working. Stay in shelters!" Mayor Vitali Klitschko said in a post on the Telegram messaging app.
Reuters' witnesses heard blasts in what sounded like air defense units in operation.
Polish and allied aircraft were activated early on Sunday to ensure the safety of Polish airspace after Russia launched air strikes targeting western Ukraine, the Operational Command of the Polish armed forces said.
"The steps taken are aimed at ensuring security in the regions bordering the areas at risk," the Command said on X.