(CNN)-- The Combined Maritime Information Center, overseen by the US Navy, reported that the southern Omani route in the Strait of Hormuz remains open to two-way navigation, despite Iran's announcement of closing the vital waterway.

The center said in an advisory note published Sunday: 'US forces are prepared to maintain freedom of navigation and protect legitimate trade, in accordance with international law. The southern route in the Strait of Hormuz remains open.'

It added that the level of security threat in the strait remains 'severe,' despite the southern route remaining open to navigation.

Iran's Revolutionary Guard Corps had announced early Sunday morning local time the closure of the Strait of Hormuz, after firing a warning shot toward a ship that it said was attempting to cross the waterway via an unauthorized route.

The United Kingdom Maritime Trade Operations (UKMTO) also reported Sunday the rescue of a container ship's crew that suffered damage near the Strait of Hormuz, after they were forced to abandon it.

The authority had reported about five hours earlier that a fire broke out on the ship after its stern sustained damage while sailing east of Oman.