Iran frees US sailors held in Gulf after incursion

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 on 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.

A Pentagon statement said the sailors had been safely returned, and that an investigation was underway as to how they entered Iranian waters.

The tentative and still largely potential softening of relations between Washington and Tehran in the wake of the nuclear deal seems to have passed a delicate initial test.

The Tehran authorities have quickly accepted that the US patrol boats strayed into their waters by accident and the crews - according to Iranian State Television - have now been released.

The process to begin lifting the sanctions imposed on Iran due to its nuclear activities is expected to get under way at the end of this week.

There are many conservatives and hardliners in both countries who would dearly love to sabotage the deal and consequently both governments may well have been eager to get this episode resolved as quickly as possible.

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.