An investigation has been launched after a Royal Navy sailor was found dead in a residence in Sweden.
Four people, including a 20-year-old British man, were arrested but have now been released, according to the country's prosecutor.
Those arrested also included two men and one woman who are all Swedish.
A Royal Navy spokesperson said: "We are aware of an incident in Stockholm which resulted in the death of a serviceperson.
"We continue to assist local authorities in their enquiries, and it would be inappropriate to comment further.
"Our thoughts and sympathies go out to the family and friends."
The sailor's next of kin have been informed.
The Royal Navy was taking part in a mock invasion exercise, called Aurora, where they defended Sweden's coastline. The military drill took place from 17 April to 11 May.
The exercise, led by HMS Albion, also included forces from France, Germany, Estonia, Finland, Latvia and Lithuania, as well as the UK and Sweden.
Exercise Aurora was "the largest Swedish national defence exercise in more than a quarter of a century".