Iran has released 10 US sailors held for entering its territorial waters, in a swift resolution of an incident that tested newly-improved US-Iranian ties.
They were detained Tuesday after one of their two vessels broke down during a training mission in the Gulf.
Iranian state media said the group was released into international waters after apologising.
It comes at a sensitive time, as the US and Iran try to implement the deal on Iran’s nuclear activities.
The incursion was “unintentional”, a statement from the Revolutionary Guards quoted by state media said.
Earlier, the naval commander of the Guards, General Ali Fadavi, said investigations found a navigational failure was to blame.
“We have concluded that passage of Americans in our territorial waters was not a hostile passage or for espionage or similar acts,” he told Iranian television.
A Pentagon statement said the Navy sailors had been safely returned, and that an investigation was under way as to how they entered Iranian waters.
“Around the world, the US Navy routinely provides assistance to foreign sailors in distress, and we appreciate the timely way in which this situation was resolved,” said Defence Secretary Ash Carter.
US Secretary of State John Kerry called Foreign Minister Javad Zarif shortly after the incident. The pair developed a personal rapport during the nuclear talks.
Those detained – nine men and one woman – were taken to Farsi Island, in the middle of the Gulf, where Iran has a naval base.
Pictures published on the Revolutionary Guards’ website showed the group sitting on a Persian rug, with the one female member wearing a headscarf.
US opponents of the nuclear deal, which will see Iran limit its nuclear activities in exchange for the lifting of sanctions, had expressed outrage at the sailors’ detention.
“Iran is testing the boundaries of this administration’s resolve,” said Marco Rubio, who is in the running to be the Republican party candidate.
Iran’s deputy nuclear chief has meanwhile denied a report the Arak heavy-water reactor had been decommissioned, which would be a final step towards implementation of the nuclear deal.
Iranian state media’s coverage of the incident has been studiously restrained and measured in tone.
The usual pejorative terms usually reserved for the US and other Western powers – such as “global arrogance” and “enemies” – have been conspicuous by their absence.
State TV and radio reports did highlight that the US incursion had been “illegal” and that Tehran wanted an apology, later reporting that it had got it.
The mood music was far less tense and confrontational than during the capture of British sailors in in 2007, with Iran insisting they strayed into its water – an accusation London denied.
Then, the Iranian media initially accused the UK servicemen of spying, and later mockingly reported that one of them had cried when his music player was confiscated.
Iran’s influential Revolutionary Guard – tasked with protecting the country’s 1979 Islamic revolution – has strongly defended Iranian sea borders in the past.
Fifteen British sailors and marines were held for 13 days in 2007 after they were captured in a disputed area between Iran and Iraq.
Despite last year’s breakthrough nuclear deal tensions remain between the US and Iran.
In December, Iran’s navy conducted rocket tests near US warships in the Strait of Hormuz, something the US called “highly provocative”.