NEW YORK and LONDON -- Polish airspace was violated by at least 19 Russian drones overnight, the country's prime minister said, in a torrent of activity that triggered a response from the NATO country's air force, which scrambled and downed several of the drones.

Multiple Russian drones crossed into Poland in what European officials described as a deliberate provocation, causing NATO to send fighter jets to shoot them down.

NATO surveillance planes and jet fighters are regularly deployed above Poland when large attacks on Ukraine threaten to spill over into allied territory, but the direct engagement marked a significant escalation in the game of cat-and-mouse between Russian drones entering alliance airspace and NATO aircraft sent to deter them.

The Polish military called the incursions an “act of aggression.” It said the drones crossed the border during a wave of Russian strikes in Ukraine.

Poland shot down suspected Russian drones in its airspace on Wednesday with the backing of aircraft from its NATO allies, the first time a member of the Western military alliance is known to have fired shots during Russia's war in Ukraine.