Iranian vessels fired upon a cargo ship flagged to the Marshall Islands Tuesday morning, forcing the ship to travel deeper into Iranian waters — and setting off another round of tensions between Iran and the US.

Col. Steven Warren, Pentagon spokesman, confirmed that Iranian patrol vessels intercepted the shipping vessel Maersk Tigris around 5 a.m. Washington time. At that time, the vessels ordered the ship to travel deeper into Iranian waters. It is not clear if the Maersk had inadvertently traveled into Iranian territory.

When the Maersk did not respond immediately, the Iranian vessels fired shots across the bow of the cargo ship, which then complied with the order. The Iranian forces then boarded the vessel. […]