British special forces stormed a Greek-operated oil tanker in the English channel on Sunday to wrest control of the vessel from seven stowaways who threatened the crew in a suspected hijacking.
Troops from the Special Boat Service, a navy special forces unit, boarded the Nave Andromeda near the Isle of Wight off southern England.
Defence Secretary Ben Wallace and Home Secretary Priti Patel authorised the troops to board the ship "to safeguard life and secure a ship that was subject to suspected hijacking", the Defence Ministry said.
"Armed forces have gained control of the ship and seven individuals have been detained," the ministry said.
"Initial reports confirm the crew are safe and well."
The 228-metre Nave Andromeda had been sailing to a refinery at the south coast port of Southampton but the captain radioed for help earlier on Sunday, Isle of Wight radio said.
Upon finding the stowaways, crew members tried to lock them inside the ship’s cabin, and were reportedly met with threats to kill.
In a desperate Mayday call, the ship’s captain reportedly said he feared for his life and told an operator: "I'm trying to keep them calm but please send help."
Mr Wallace said the operation had taken place "in dark skies, and worsening weather".
"We should all be grateful for our brave personnel," he said.
"Today we are thankful for the quick and decisive action of our police and armed forces who were able to bring this situation under control," Ms Patel said on Twitter.
The ministry declined to confirm or deny the involvement of the troops, in line with British government policy of not commenting on special forces operations.
Police said the crew had been subjected to threats from the stowaways and that they were working with the coastguard and border forces to resolve the situation.
"No one has been reported injured," a police spokesman said.
Refinitiv vessel tracking data showed the Liberia-flagged Nave Andromeda had been expected to arrive in the English port of Southampton at 10.30am on Sunday.
The Nave Andromeda's registered owner is Folegandros Shipping Corp, and the vessel is managed by Greek shipping company Navios Tankers Management, according to Refinitiv.
The Isle of Wight MP, Bob Seely, told Sky News that the ship had dropped anchor despite the skipper being told not to.
"The ship may be now under the control of stowaways on the ship," Mr Seely said.
"I suspect because of the nature of this it will be treated as marine counter-terrorism and the number of people in the UK who do that are very limited.
"And the relevant units will be looking at options, no doubt, as to what we could be doing."
The Isle of Wight, England's largest island, is a short boat trip from the mainland and is popular with day-trippers.
Associated British Ports, which runs the port at Southampton, declined to comment.
Those arrested were reportedly Nigerian stowaways.
The incident comes nearly two years after four stowaways from Nigeria and Liberia ran amok on a container ship after they were discovered by members of the crew.
The men, who had boarded at Lagos, demanded to be dropped off in Britain when the ship reached the Thames Estuary.
They threatened the crew of the Italian cargo ship who barricaded themselves on the bridge.
But the stowaways were arrested after British armed troops stormed the ship.
The four were later jailed for affray but were cleared at a trial in London of trying to hijack the ship.