Poland and NATO scrambled fighter jets early on Sunday after Russia launched strikes in Western Ukraine, Poland's armed forces said.
While the entire Ukraine was under an air raid alert, the airspace near the southeastern Polish cities of Lublin and Rzeszow was closed until at least 0400 GMT due to "unplanned military activity related to ensuring state security", flight tracking site Flightradar24 reported.
Kyiv Mayor Vitali Klitschko said the city had come under a "massive attack", with a five-story building partially destroyed due to drone debris. At least three people were taken to hospital, he added.
The air around the Polish border visibly pulsed with tension in the early hours of Sunday. From the east, distant, muffled explosions could be heard, periodically interrupting the silence. The sky in the direction of Ukraine was illuminated by flashes, lighting up the darkness.
The events are another example of the escalation of tension following the repeated Russian violations of the airspace of NATO countries this month. The actions of the Russian side provoked an immediate reaction and increased vigilance from NATO.