NATO allies Poland and Romania both scrambled fighter jets to respond to Russian drone and missile attacks in Ukraine on Saturday, as the alliance looks to bolster its defensive options in response to repeated violations of allied airspace by Russian munitions.

The Polish military said no airspace violations were recorded on Saturday after jets were deployed in the airspace along the border with Ukraine. Polish Prime Minister Donad Tusk reported in a post to X that defenses “reached the highest state of readiness” in response to “the threat posed by Russian drones operating over Ukraine near the border with Poland.”

But, farther south along NATO’s eastern flank, a Russian drone did violate Romanian airspace, according to a statement published by the Defense Ministry in Bucharest.

Two F-16 fighters were dispatched “to monitor the air situation on the border with Ukraine, following Russian air attacks on Ukrainian infrastructure on the Danube,” the ministry said. The Danube River forms the border between Romania and Ukraine. Russian drones and missiles have repeatedly targeted Ukrainian port and shipping targets there.

The aircraft “detected a drone in national airspace, which they tracked to approximately 20 kilometers southwest of Chilia Veche, where it disappeared from radar,” the ministry said. “The drone did not fly over populated areas and did not pose an imminent danger to the safety of the population.”

The Defense Ministry told ABC News that its “preliminary reports show the drone flew back to Ukraine. A search team have been dispatched to look out for potential debris.”

“President of the Republic of Poland Karol Nawrocki signed a resolution expressing consent for the stay on the territory of the Republic of Poland of a component of the armed forces of foreign States-Parties to the North Atlantic Treaty Organization as reinforcement of the Republic of Poland within the framework of the ‘Eastern Sentry’ operation,” Poland’s National Security Bureau said in a social media post on Sunday.

“The President’s resolution is classified,” the post added.

Saturday’s violation of Romanian airspace by a Russian drone was the eleventh such incident since the start of Moscow’s full-scale invasion of Ukraine in February 2022, according to data provided to ABC News by the Defense Ministry in Bucharest.

One day before the latest violation, a ministry spokesperson said there had been approximately 50 attacks involving Russian drones on Ukrainian territory near Romania’s borders to date, of which 30 saw drone debris falling on Romanian territory.

In 10 instances, Russian drones “briefly penetrated Romania’s airspace,” the spokesperson said.

After Saturday’s incident, Romanian Defense Minister Ionut Mosteanu said in a post to X that Bucharest “condemns Russia’s reckless behavior, which threatens regional stability. Together with our NATO allies, we remain vigilant and ready to defend every inch of allied airspace.”

Romania is yet to shoot down any Russian drones. The first instance of NATO nations downing drones came last week, when Polish and Dutch fighters destroyed three Russian drones over Poland. At least 19 drones penetrated Polish airspace in that instance, according to Warsaw.

The Romanian defense ministry spokesperson told ABC News that the country has adopted “a completely new legislative approach” since the outbreak of Russia’s invasion of Ukraine, which includes the use of “non-kinetic (e.g. taking control of the drone through specific devices) and kinetic (their destruction) measures.”

“The aircraft that cannot be neutralized by non-kinetic measures may be destroyed, depending on the level of threat, if there is a real danger to national security, the people’s lives or property,” the spokesperson said.

Ukrainian President Volodymyr Zelenskyy said in a post to X that the Russian drone that violated Romanian airspace on Saturday flew around six miles into the country, operating in NATO airspace for around 50 minutes.

“The Russian military knows exactly where their drones are headed and how long they can operate in the air,” Zelenskyy wrote. “Their routes are always calculated. This cannot be a coincidence, a mistake, or the initiative of some lower-level commanders.”

“It is an obvious expansion of the war by Russia — and this is exactly how they act,” he added. “Small steps at first, and eventually big losses.”

Ukraine’s air force, meanwhile, said Russia launched 58 drones and one missile into the country overnight into Sunday morning. Air defenses downed or suppressed 52 drones, the air force said, with the missile and six drones impacting across three locations. Falling drone debris was reported in two locations, the air force said.

Russia’s Defense Ministry, meanwhile, said its forced downed at least 103 Ukrainian drones overnight into Sunday.