According to an announcement by the US Air Force on Friday, US aircraft units from the 131st Fighter Squadron at Barnes Air National Guard Base in Massachusetts and the 194th Fighter Squadron at Fresno Air National Guard Base in California will support NATO air surveillance missions in Iceland and conduct flying training in the Netherlands.

The F-15s are part of the US's Theater Security Packages, a rotational force used to augment existing Air Force capabilities in Europe, the Air Force said.

"Russia's increased patrols with fighters, bombers and submarines in the North Atlantic have brought new attention to the region and the need for NATO to have a presence there as well," said Magnus Nordenman, director of the Transatlantic Security Initiative at the Atlantic Council.

The aircraft are scheduled to remain in Europe through September.

The US used to have an air base in Iceland during the Cold War but that base was closed in 2006.

In February, the US also said it will send six F-15s to Finland as part of a program initiated in 2014 to reassure NATO allies after Russian military intervention in Ukraine. These aircraft are set to deploy next month.

Tensions increased between Russia and the West in March 2014 after Ukraine’s Black Sea peninsula of Crimea jointed the Russian Federation following a referendum. NATO eventually severed all military cooperation with Moscow over a crisis in Ukraine in April 2014.

Ties further soured after the US and its European allies accused Russia of destabilizing the situation in Ukraine and imposed a number of sanctions against Moscow over the crisis in Russian-speaking regions in eastern Ukraine. Russia has rejected the accusations.

In the appraisal, Russia also accused the US and the European Union of supporting an "anti-constitutional coup d'etat in Ukraine", which led to a divide in the Ukrainian society, as well as the military conflict in east of the country; Press TV reported.

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