By Emma Pinedo and Jonathan Saul
MADRID (Reuters) - Spain has detained and fined a Maltese-flagged oil tanker it says discharged oil in open waters near the northeastern port city of Tarragona, a transport ministry department said.
Spain's Mediterranean and Atlantic coastlines have become hubs for shipping activity including the transfer of oil known as ship-to-ship (STS) operations, which industry sources say are becoming an increasing safety concern.
Spanish authorities said they had intercepted the Lagertha after a discharge of hydrocarbons was detected by aircraft sensors and satellite radar on Feb. 11.
"The slick, in the stern area of the vessel, extended over an area of 12.7 square kilometres," Spain's Merchant fleet, a transport ministry department, said on Tuesday in a statement.
It said the vessel was being detained until the owners paid bail of 100,000 euros ($106,680), adding that on the basis of the evidence, authorities will begin disciplinary proceedings.
The Merchant Fleet told Reuters that the Lagertha was in open sea and it was unable to measure if there was any environmental damage.
The vessel's Turkey-based manager Besiktas Shipping Group - according to shipping databases and its website - did not immediately respond to a request for comment.
In 2021, another tanker was intercepted by Spain for illegally discharging oil at sea over some 55 square kilometres off the coast of La Palma in the Canary Islands.
Separately, the Merchant Fleet told Reuters that it had detained another tanker, the Elephant, on Feb. 14 after authorities detected "deficiencies of a technical and documentary nature" during an inspection in the northwest port of Ferrol and also for failure to notify Spain's maritime administration with documents related to STS operations.
The Elephant's owner, according to shipping databases, is Vietnam-based Hung Phat Maritime Trading, which could not immediately be located by Reuters for comment.
Spanish officials said the Elephant had transferred a cargo to the Singapore-flagged tanker Maersk Magellan, which was banned from Spanish ports earlier this month.
Authorities in Spain said the Elephant had previously loaded a cargo from the Cameroon-flagged Nobel. This vessel, they said had been working under a Russian flag until July 1, 2022, which was in breach of European Union sanctions.
Denmark's Maersk Tankers declined to comment last week about the Elephant, but said that official documents showed the cargo it moved to the Maersk Magellan was of Turkish origin. The company operates the Maersk Magellan.
Trade in oil and oil products linked to Russia has been complicated by the Group of Seven's imposition of a price cap on Russian oil in December and separate EU measures to prohibit the import of Russian crude and oil products.
($1 = 0.9374 euros)
(Reporting by Emma Pindeo in Madrid and Jonathan Saul in London; Editing by Alexander Smith)