In a statement, the Navy explained that it is "a conventional submarine capable of remaining submerged for long periods and firing missiles capable of hitting ships or targets on land".

The submarine sailed accompanied by the "high-sea tugboat Evegeny Churov".

The vessels began sailing along the continent's Exclusive Economic Zone (EEZ) on Friday, September 6, and finished on Sunday morning, "heading towards the Mediterranean Sea”.

The NRP Setúbal was involved in the operation, which "accompanied the Russian Federation vessels".

In the note, sent to newsrooms, the Navy stressed that "through these monitoring and surveillance actions, it guarantees the defense and security of maritime spaces under national sovereignty, jurisdiction or responsibility, contributes to the protection of Portugal's interests and its critical infrastructures", also ensuring "compliance with the international commitments assumed within the framework of the Atlantic Alliance".