Update 2: Curiously, while we were confident Iran would deny the report first, it was in fact the US: US NAVY DENIES CONFRONTATION WITH IRANIAN MILITARY: CNBC
Update: WHITE HOUSE REFERS COMMENT ON IRAN SHIP CAPTURE TO DEFENSE DEPT
Moments ago according to Saudi-owned Arabiya news, Iranian forces have seized a US cargo ship, which has some 34 American sailors, which they have taken to the port of Bandar Abbas. Iran's Farsnews confirms the Arabiya report, stating that "a US cargo ship with 34 crew was stopped and seized by Iranian Navy warships on Tuesday. The Iranian Navy has confiscated the American trade vessel with all its 34 crew for trespassing on Iran's territorial waters in the Persian Gulf."