US surveillance planes have apparently kept a close eye on Russian warships in the Mediterranean and the Russian naval base in the Syrian city of Tartus, with the US Navy's Р-8А Poseidon aircraft spotted over the Syrian coast on Friday and two US spy planes carrying out surveillance missions to the east of Crete on Thursday, media reports indicate.

On Friday, a spy plane with the serial number 168761 is said to have taken off from NATO Base Sigonella in Sicily, Italy. The Р-8А Poseidon, tasked with conducting anti-submarine warfare, anti-surface warfare, shipping interdiction and electronic signals intelligence, then circled over the Syrian coast near Tartus, home to the Russian Navy's maintenance and support facility.

A day earlier, the two Р-8А Poseidon planes appeared to have been flying in the area where a group of Russian military vessels, led by the Admiral Kuznetsov aircraft carrier, is currently located.

Other ships in the group include the Pyotr Veliky battle cruiser, the Severomorsk and Admiral Kulakov anti-submarine destroyer, as well as support vessels. Frigate Admiral Grigorovich armed with Kalibr cruise missiles was supposed to join the aircraft carrier group on November 3.

In addition, the large landing ship Caesar Kunikov and a supply vessel are believed to have entered the Mediterranean on the same day. The warships are heading to Tartus.

This week, US surveillance planes have conducted daily missions over the eastern Mediterranean, prompting some to link this activity to Russia's increased naval presence in the region.