The US military has sent aircraft to monitor the presence of a fugitive oil tanker off Ireland’s west coast as the vessel sails for safe harbour in Russia.

On Sunday afternoon and evening, the US deployed several maritime surveillance aircraft about 400km west of Ireland near the suspected area of the Russian flagged tanker.

The aircraft took off from Nato bases in Britain and Iceland. The oil tanker, the Marinera, which until a few days ago was registered as a Guyana-flagged vessel called the Bella 1, has been pursued by US naval forces since mid-December when it prepared to collect a consignment of oil from Venezuela.

The vessel fled into the Atlantic. While at sea, it changed its name and its flagged country to Russia. Russia has accepted the ship on to its shipping registry and has asked the US to cease its pursuit.

The ship’s crew also painted a crude Russian flag on its side in an attempt to deter its American pursuers.

For the last three days, the ship has been sailing northeast towards the Irish exclusive economic zone (EEZ), with the apparent intention of seeking sanctuary in a Russian North Sea port. By Sunday night, it was about 450 nautical miles off the Irish west coast.

Its current direction suggests it will skirt the outer north-western edge of the Irish EEZ on its way to Russia. Satellite data seen by The Irish Times does not show any US Navy or Coast Guard ships in pursuit. However, US P-8 Poseidon anti-submarine aircraft have deployed from the UK and Iceland and are patrolling off the Irish west coast in the area of the Marinera. The aircrafts’ paths differ significantly from regular Atlantic patrols carried out by US aircraft.

There has also been unusually large movements of military cargo aircraft from US military bases to UK airbases on Sunday. Some of these aircraft took off from US special forces bases and some carried helicopters, raising the possibility that the US is still considering seizing the Marinera at sea by force.

However, it is also possible the aircraft movements relate to unscheduled training exercises with UK forces or separate operations.

Irish officials are aware of the Marinera’s path off the west coast. So far, no Irish air or naval assets have been deployed in response.

The Trump administration has put sanctions on the export of oil from Venezuela and to date has seized two of its tankers.

The US mounted a raid on the Venezuelan capital of Caracas on Saturday morning, carrying out numerous strikes and capturing Nicolas Maduro, the country’s president.

Ships are entitled to the protection of the country they are registered in. The acceptance of the ship on to the Russian registry indicates Moscow has accepted this position.

The ship’s passage presents a highly unusual situation for Irish authorities.

The Defence Forces and Irish Coast Guard have been responding to a dramatic increase in shadow-fleet vessels appearing in the Irish EEZ over the last year.

However, they have not yet been forced to deal with an unflagged oil tanker being actively pursued by another country through Irish waters while claiming the protection of a separate country.