LONDON (AP) -- Britain on Monday summoned the Russian ambassador in London following Moscow's "unprecedented violation" of NATO airspace, as the U.K. announced it would send fighter jets to help defend Polish airspace.

The Foreign Office called the incursions into Polish and Romanian airspace in recent days "unacceptable" and summoned Andrei Kelin, the Russian ambassador.

"Significant and unprecedented violation of Polish and NATO airspace by Russian drones last week, followed by a further incursion into Romanian airspace on Saturday, was utterly unacceptable," the ministry said in a statement.

"Russia should understand that its continued aggression only strengthens the unity between NATO allies and our determination to stand with Ukraine, and any further incursions will again be met with force," the ministry added. "Russia must end its illegal war on Ukraine."

"The U.K stands united with Poland, Romania, Ukraine and our NATO allies in unreservedly condemning these reckless actions," the office added.

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

Russia said Poland wasn't targeted, and Moscow's ally Belarus said the drones went astray because they were jammed. But European leaders have expressed certainty that the incursion was deliberate, underlining long-held concerns about the expansion of Russia's more than three-year war in Ukraine.

Polish airspace has been violated several times since Russia's full-scale invasion of Ukraine in 2022, but there has been nothing on the scale of Wednesday's violations in Poland or in any other NATO country.

Romania said Saturday it deployed two F-16 jets to intercept a drone that briefly entered its airspace. The country's defense ministry said the drone did not fly over inhabited areas and did not represent an imminent danger to the public.

Britain's military said Monday that Royal Air Force fighter jets will join several other European nations in aur-defense missions over Poland.

Britain's Defense Ministry said the Typhoon jets will join planes from Denmark, France and Germany in the mission, dubbed Eastern Sentry, which involves extra European fighter jets, a warship and air defense systems along with existing air policing and ground defenses.

Prime Minister Keir Starmer said "Russia's reckless behavior is a direct threat to European security and a violation of international law, which is why the U.K. will support NATO's efforts to bolster its eastern flank through Eastern Sentry."

UK summons Russian ambassador over violation of NATO airspace and sends jets to Poland