This is being reported with few details by sites like the Telegraph, however here is a short Arabic report from Al Arabiya (translated by Bing) that gives a few more details on how Iran has fired on a US cargo ship and taken it captive, along with 34 Americans on board:
The Iranian force seized a US cargo ship carrying 34 Americans and taken to the Iranian port of Bandar Abbas.
Reports said that the Iranian force fired at the ship before that.
UPDATE: The BBC is reporting that the US denies
American officials have denied media reports that a US cargo ship had been seized by the Iranian navy.
An American official told Reuters there were “no indications so far” of any US ship being directed into an Iranian port.
However, a Pentagon spokesman said a Marshall Islands-flagged ship had been boarded by the Iranian navy.
UPDATE II: It’s now being widely reported that this ship was indeed from the Marshall Islands and has NO AMERICANS ON BOARD.
UPDATE III: Here’s the lowdown on what actually happened and it wasn’t as it was first reported:
WASHINGTON TIMES – Iranian troops boarded a cargo vessel early Tuesday morning after firing shots at the ship, prompting the U.S. to send assets to the ship’s defense.
The Pentagon said at least five Iranian patrol vessels approached the Marshall Islands-flagged Maersk Tigris cargo ship at 5:00 am eastern time as it was transiting the Straight of Hormuz and directed the ship to proceed further into Iranian waters.
When the ship’s master declined, the Iranian ship fired shots across the bow of the cargo vessel, Pentagon spokesman Col. Steve Warren said. After shots were fired, the ship proceeded into Iranian waters near the vicinity of Larak Island. It was boarded by members of the Iranian military and is now unable to leave Iranian waters.
The Marshall Islands gained independence from the United States in 1986, but the U.S. continues to have “full authority and responsibility for security and defense of the Marshall Islands,” according to the State Department’s website.
The Maersk Tigris issued a distress call, prompting U.S. Naval Forces Central Command to send the U.S. destroyer Farragut to the site as well as aircraft to observe the interaction, Col. Warren said. The destroyer is currently on the way, with no clear timetable of when it will arrive on the scene.
The U.S. assets are being sent to “monitor the situation,” Col. Warren said.
It is unclear if the Maersk Tigris inadvertently entered Iranian waters. There are no Americans aboard the cargo ship and currently no injuries reported among the crew, Col. Warren said.