Military forces from across Europe have started deploying to NATO's eastern flank in a new military activity called "Eastern Sentry."

Harry travelled to Kyiv with a team from his Invictus Games Foundation following an invitation from the Ukrainian government and Olga Rudneva, chief executive of the Superhumans Centre, an orthopaedic clinic and rehabilitation centre for adults and children affected by the war in Ukraine.

In the years since Russia invaded Ukraine, NATO has focused on defending its own territory first and resisted lower-level harassment from Russia, like acts of sabotage and intimidation.

A restricted zone in the eastern part of the NATO country is in place following Russian drones entering its airspace.

Polish airspace was violated by Russian drones 19 times overnight, with NATO fighters shooting several of them down.

Russia's electronic warfare capabilities are increasingly targeting GPS systems across Europe, causing disruptions to civilian and military aviation. A recent incident involving European Commission President Ursula von der Leyen's plane losing GPS navigation highlights the vulnerability.

Poland has accused Russia of sending several drones into its territory, with prime minister Donald Tusk saying the country is the closest it has been to armed conflict since the Second World War.

WARSAW, Poland (AP) — The downing of Russian drones over Poland, the first direct encounter between NATO and Moscow since the war in Ukraine began, jolted leaders across Europe on Wednesday and raised urgent questions about how prepared the alliance is against growing Russian aggression.

NATO fighter jets shot down multiple Russian drones that violated Polish airspace during an attack on neighboring Ukraine early on Wednesday, as the military alliance denounced Moscow for “absolutely dangerous” behavior that ratcheted up tensions to a new level.

Whether the drone incursion was deliberate or accidental, Moscow will be watching Nato's response to it closely.