HELSINKI (AP) — A news conference at a NATO air base in Lithuania featuring Lithuania's president and Spain's prime minister got abruptly cut off Thursday when the pair of Spanish fighter jets serving as the leaders' backdrop were scrambled to monitor errant military aircraft in the skies above the Baltics.

The Spanish government said an unidentified plane prompted the alert and briefly interrupted remarks by Lithuanian President Gitanas Nauseda and Spanish Prime Minister Pedro Sánchez. Spanish media reported that the plane was Russian, but the government’s statement didn’t specify.

A NATO official who spoke on customary condition of anonymity told The Associated Press later Thursday that Spain's jets took off "to identify two aircraft flying into the Baltic Sea area.” The planes were two Russian Su-24 combat jets heading northeast, the official said.

"Those two Russian jets did not file a flight plan, did not have their flight transponder on, or talk to traffic controllers,” the official said.

The Russian Defense Ministry said the two Su-24 bombers flew a regular training mission over neutral waters of the Baltic on Thursday. “The flight was performed in strict accordance with international rules of using airspace and without violation of any country's borders,” the ministry said in a statement.

Amid Russia-West tensions, both Russia and NATO have regularly scrambled fighter jets to identify and shadow the other party's aircraft.

Nauseda and Sánchez were speaking with two Spanish air force Eurofighter Typhoons behind them at the base in the town of Siauliai when security officials suddenly interrupted the leaders as crews scrambled to get on the fighter jets, live footage from the press conference showed.

“Our press conference was interrupted by a real call....You see, everything works great. I can confirm that the fighter jets took off in less than 15 minutes" of receiving the alarm, Lithuanian public broadcaster LRT quoted Nauseda as saying after the incident. "Thanks to Pedro (Sánchez), we have really seen how our air policing mission works.”

Sánchez told reporters when the news conference resumed: “We have seen a real case of what usually happens that precisely justifies the presence of Spanish troops with the seven Eurofighters in Lithuania.”

The three Baltic nations — Estonia, Latvia and Lithuania — joined NATO in 2004 and have no fighter jets of their own. NATO has the responsibility of policing their airspace on a rotational four-month basis from the base in Siualiai and in Amari, Estonia.

Aircraft that member nations assign to NATO missions are on standby around the clock every day of the year. They were scrambled about 400 times in Europe last year, mostly in response to movements by Russian warplanes.

“This demonstrates once again the importance of NATO’s air policing mission, which has been running for 60 years to keep our skies safe. It also shows the skills of our pilots and the close coordination among NATO allies,” NATO spokesperson Oana Lungescu said.

Lithuanian Defense Minister Arvydas Anusauskas confirmed that an alarm signal was triggered at the base in his country and posted a video on Facebook of one of the departing Spanish fighters.

Sánchez is on the final day of a three-day trip to the Baltic region and earlier met with officials in Estonia and Latvia.

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Cook reported from Brussels. Aritz Parra in Madrid and Vladimir Isachenkov in Moscow contributed to this report.