Iran's navy said Thursday it saved an American-flagged cargo ship that was being attacked by pirates in the Gulf of Oman.

An Iranian warship responded to a distress signal from the US-flagged Maersk Texas, a cargo ship of 150 metres (500 feet) and 14,000 tonnes, which was besieged by "several pirate boats," the navy said in a statement reported by the official IRNA news agency.

The cargo vessel "was saved by the navy of the Islamic Republic of Iran" on Wednesday, IRNA added.

The pirates "fled the scene as soon as they spotted the presence" of the warship. Maersk Texas "thanked the Iranian navy and sailed towards its destination safely," it added.

It was the first time the Iranian navy protected a US ship from pirates.

Maersk Line told AFP that its vessel, Maersk Texas, had "thwarted an attack by multiple pirate skiffs at noon local while transiting the Gulf of Oman, northeast of Fujairah" but denied it had been helped by the Iranian navy.

"Maersk Texas heard from the Iranian navy over radio to the initial distress call, but our vessel received no assistance from the Iranian navy," spokesman Kevin Steers said in an email sent to AFP in Washington.

"All hands onboard are safe and unharmed, and the vessel is proceeding on its voyage," he added.

Iran's navy keeps a presence in Gulf of Oman to protect cargo ships and transiting oil tankers and also defend the country against potential threats.

According to Iranian commanders, Iran's navy have carried out hundreds of anti-piracy operations, engaging in hundreds of armed clashes with pirates in the past three years.

The US navy patrolling the area have on a number of occasions rescued Iranian ships. The latest incident was in January when a US warship secured the release of 13 Iranian fishermen near the entrance to the Gulf who had been held captive by pirates for 45 days.