Ukraine has accused Russia of pounding the country with "hundreds" of drones and missiles overnight, killing at least four people in the capital.
The attacks came after Russia warned NATO against taking sterner action in response to alleged incursions into airspace covered by the military alliance.
Ukrainian President Volodymyr Zelenskiy said on Sunday that around 500 drones and more than 40 missiles had been launched during the attack.
"Moscow wants to continue fighting and killing and deserves only the harshest pressure from the world," he said on the Telegram app.
The barrage also followed the revelation by Mr Zelenskyy that Kyiv had received a US-made Patriot air defence system from Israel for use against Russian assaults.
"Russia launched another massive air attack on Ukrainian c