A Sukhoi SU-30 fighter and an IL-78 tanker passed through Lithuanian airspace for 700 metres (2,300 feet) before leaving it 18 seconds later, probably during aerial refuelling training, according to a short statement from the NATO member country.

Two Spanish airforce Typhoon Eurofighters -- part of a NATO air patrol mission in the Baltic -- were quickly deployed.

The three Baltic countries, all NATO members and firm supporters of Ukraine, border either Russia or its ally Belarus and have been exposed to violations of their territory by Russian planes or drones.

In September, three Russian MiG-31 fighter jets entered Estonian airspace over the Gulf of Finland and remained there for approximately 12 minutes.

This incident prompted Tallinn to request an extraordinary meeting of the UN Security Council and the activation of Article 4 of the Atlantic Treaty, which provides for consultations between allies in the event of a threat to one of its members.