A US Navy aircraft flew over Irish sovereign airspace on Monday afternoon to intercept a ship targeted by the Trump administration as part of its military action against Venezuela.

The P-8 Poseidon anti-submarine aircraft was sent to an area of the north Atlantic containing the Marinera, a sanctioned oil tanker that has been pursued by US forces since it tried to collect a consignment of oil from Venezuela in mid-December.

For two weeks, US naval vessels chased the ship northeast across the Atlantic. During its journey, it changed its flag and registration from Guyana to Russia in an apparent attempt to deter its pursuers. It also changed its named from the Bella 1 to the Marinera.

Russia then requested the US to call off its pursuit. On Monday night, the Marinera was sailing north, about 600km off the Irish west coast. Its course suggests it intends to seek sanctuary in a northern Russian port.

Since the ship arrived in the North Atlantic, the US has sent several P-8 aircraft to keep it under surveillance. These aircraft have been deployed from Nato bases in Iceland and the UK.

[ US military monitors oil tanker off Irish coast as it sails towards RussiaOpens in new window ]

Until Monday, these aircraft avoided entering Irish airspace in line with standard practice. However, on Monday afternoon a P-8 departed from RAF Mildenhall in Sussex and travelled across the middle of Ireland to the North Atlantic. It remained in Irish airspace for about 40 minutes.

It then patrolled the area containing the Marinera for nearly five hours before returning by the same route over Ireland and landing in the UK.

The aircraft’s route was highly unusual. Under long-standing Irish policy, foreign military aircraft are not permitted to use Irish airspace while on active military operations.

Permission is routinely granted to military flights to pass through or refuel in Ireland. However, according to repeated Government statements, diplomatic clearance is only given if “the flight in question does not form part of a military exercise or operation”.

[ Irish military aircraft sent to monitor fleeing oil tankerOpens in new window ]

Irish and US sources said permission had been sought for the flight at a Government level. The aircraft also received clearance from Irish air traffic control (ATC). However, it is not clear how this was justified under current Irish Government policy.

The Department of Foreign Affairs did not respond to requests for comment.

A review of air traffic control communications confirms the P-8 travelled across Ireland for operational purposes. A member of the flight crew told an ATC officer at about 1.10pm that the aircraft was heading for a waypoint off the west coast, at which point it would go “operational”.

He said the aircraft would have a “due regard” status, an aviation term often used by military aircraft to indicate they would be undertaking unusual operations.

At about 5.45pm, the aircraft contacted Irish ATC again stating it was still “operational” but would soon cross Ireland again.

A spokesman for the US European Command said details on the flight are “not releasable at this time”.

He said flights by US forces in Europe take place “in accordance with access, basing, and overflight agreements with allies and partners”.

The Pentagon did not respond to request for comment.

Sinn Féin TD Donnchadh Ó Laoghaire, the party’s spokesman on defence, said the matter is highly concerning. He called for urgent clarity.

“Ireland’s sovereignty has to be respected and international law has to be respected. The Department of Foreign Affairs needs to offer clarity on whether clearance was given or not. This is an extremely serious matter and the Irish Government needs to treat it as such.”

On Monday, the Defence Forces also deployed a maritime patrol aircraft on a three-hour mission off the west coast in the same area as the P-8 and the Marinera.

A Defence Forces spokesman said it does not comment on operations but said “when necessary, specific intelligence-led maritime defence and security operations are executed as a stand-alone operation”.