In the week since NATO fighter jets scrambled to shoot down multiple dozens of Russian drones that had crossed into alliance airspace in Poland, US and Western intelligence officials have been unable to determine whether the incursion was accidental or an intentional effort by Russia to probe western air defenses and gauge NATO’s response.

President Trump warned Sunday that the US will defend Poland and the Baltic countries if Russia’s aggression escalates after a series of incursions into the airspace of the NATO allies.

"We will do more to ensure that our people are safe," Polish Deputy Prime Minister Radoslaw Sikorski told Newsweek.

On Sept. 15, Kremlin spokesperson Dmitry Peskov said, "NATO is at war with Russia. This is obvious, and it does not require any additional evidence."

The UK is not the only Nato country patrolling the eastern flank - with missions also being coordinated alongside Denmark, France and Germany.

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.

Donald Trump said he would help defend Poland and the Baltic states in the event of an escalation by Russia.

This situation brings us the closest we have been to open conflict since World War II," Polish Prime Minister Donald Tusk said.

A swarm of Russian drones flew last week into Poland in what officials there regarded as a deliberate provocation.

It comes as the UK sent fighter jets to Poland in a warning to Putin to stay out of Nato territory after repeated incursions