NATO jets have been scrambled after Vladimir Putin launched one of the heaviest drone and missile attacks on Kyiv since the start of the war.
The 'massive' air assault killed at least four people including a 12-year-old girl and left dozens injured after 500 drones and 40 missiles bombarded the Ukrainian capital and surrounding regions overnight.
Swarms of drones were launched just hours after Russian foreign minister Sergey Lavrov threatened a 'decisive response' to any action against unauthorised Russian raids into NATO airspace.
Neighbouring Poland, which shot down three of Putin's drones which infringed on their airspace earlier this month, scrambled jets early on Sunday as Russia pounded western Ukraine.
It also temporarily shut airspace near two of its southeastern cities.
The moves were preventive and aimed at securing Polish airspace and protecting citizens, in particular in areas near Ukraine, the Polish Armed Forces said.
'Due to the activity of long-range Russian air forces carrying out strikes on Ukrainian territory, Polish and allied air forces have begun operating in our airspace,' it added.
'The Operational Command of the Polish Armed Forces is monitoring the current situation, and subordinate forces and resources remain ready for immediate response.'
NATO have scrambled jets after Vladimir Putin launched one of the heaviest drone and missile attacks on Kyiv since the start of the war
Around 500 drones and 40 missiles bombarded the Ukrainian capital and surrounding regions overnight
The 'massive' air assault killed at least four people including a 12-year-old girl and left dozens injured
Poland has vowed to down any hostile objects over Ukraine as the country looks to fast-track laws giving the military greater freedom to act.
'Moscow wants to continue fighting and killing and deserves only the harshest pressure from the world,' Volodymyr Zelensky said on Saturday morning following the Russian attack.
He said the assault underlined the need for more punitive sanctions against Russia to force it to stop its aggression.
Ukrainian Foreign Minister Andrii Sybiha added: 'Putin must feel the danger of continuing this war - personally for him, his buddies' pockets, his economy, and his regime.
'That is what can make him stop this senseless war.'
The overnight barrage also injured at least 16, including three children, in the southern city of Zaporizhzhia.
In Kyiv, drones flew over the city and anti-aircraft fire rang out for several hours.
Loud explosions were also heard with the attack continuing throughout the morning.
Kyiv's Mayor Vitali Klitschko said a fire had broken out at a state cardiological hospital as a result of the attack.
Some residents fled to metro stations deep underground for safety, sleeping on makeshift beds or sitting on deck chairs following events on their phones.
Speaking before the latest assault, Zelensky said: 'Putin will not wait to finish his war in Ukraine. He will open up some other direction. Nobody knows where. He wants that.'
The warning came after Lavrov spoke at the United Nations General Assembly on Saturday as unauthorised flights into Nato's airspace have raised alarm around Europe in recent weeks.
NATO jets have downed drones over Poland while Estonia said Russian fighter jets flew into its territory.
Russia denied that its planes entered Estonian airspace and said the drones did not target Poland, with Moscow's ally Belarus maintaining that Ukrainian signal-jamming sent the devices off course.
Mr Lavrov warned that any retaliation against Russia would come with dire consequences.
'Russia has never had and does not have any such intentions' of attacking European or Nato countries,' he said.
'However, any aggression against my country will be met with a decisive response.'