Five Iranian boats fire shots in the Persian Gulf

(CNN)Five Iranian boats fired shots across the bow of a Singapore flagged cargo vessel in the Persian Gulf on Thursday in an attempt to potentially stop the ship, a U.S. official told CNN. For the first time, the incident brought another Persian Gulf nation into the recent rising maritime tensions in the region.

It is not yet clear if any of the rounds hit the Alpine Eternity. There were no U.S. citizens or cargo on board. The Pentagon is still gathering information about the incident.

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The incident began when five small fast boats, believed to be manned by Iran's Revolutionary Guard Corps Navy approached the cargo vessel just off the coast of the United Arab Emirates but in international water, the official said.

These Iranian boats are typically manned with smaller caliber weapons such as machine guns.

The Iranian boats fired across the bow, and at that point the cargo vessel turned and escaped by entering into UAE territorial waters, according to initial U.S. military reports of the incident. The UAE sent three of its coast guard boats out to the cargo vessel.

The incident began with the Iranians ordering the ship into Iranian waters. When the ships master refused, the Iranians began to fire in a way to try to disable the ship, not just as warning shots, the U.S. official said.

Several shots hit the cargo ship, but did not disable it. The ship went into UAE waters and the Iranians followed it into those territorial waters, continuing to fire, before breaking off.

The cargo ship's master did call coalition warships in the vicinity on the radio including U.S. Navy warships to ask for help when the incident began. A P-3 from a country in the region was sent overhead and the Navy began moving, but the incident was over before it could get there.

Ben Rhodes, the deputy national security adviser, said Thursday there were "no U.S. vessels or persons" involved in Thursday's incident.

He didn't have any more details of the episode, but he said those types of incidents are "exactly the type of challenge many of the GCC partners are focused on."

President Barack Obama did not discuss the incident with Gulf leaders at Camp David.

The Pentagon recently stopped escorting commercial vessels through the Strait of Hormuz and it's not clear if those operations will resume. They had been escorting commercial shipping but of two recent Iranian incidents interfering with cargo shipping in the area.