A US navy ship has rescued a 13-member Iranian crew held hostage by Somali pirates for more than 40 days in the Arabian Sea.

The USS Kidd, a guided-missile destroyer, responded after the captain of the Iranian fishing boat, Al Molai, sent a distress call, the US navy said on Friday.

"The Al Molai had been taken over by pirates for roughly the last 40-45 days," Josh Schminky, a navy criminal investigative service agent aboard the USS Kidd, said, adding that the men were held with "limitd rations and ...forced against their will to assist the pirates with other piracy operations."

A US navy team boarded the ship on Thursday and detained 15 pirates who had been holding the Iranian crew hostage and were using the vessel as a "mother ship'' for pirating operations.

A navy search and seizure team was taken by helicopter from the USS Kidd and met no resistance from the pirates, who surrendered quickly.

The US team gave the crew food, water and medical care and transferred the captured pirates to the USS John C Stennis, a nuclear-power supercarrier, where they remain.

Rescue a 'humanitarian' gesture

"This is an incredible story. This is a great story," Victoria Nuland, the state department spokeswoman, said, saying that the very same American ships the Islamic republic protested for recently travelling through the Strait of Hormuz were responsible for the Iranian vessel's recovery.

"They were obviously very grateful to be rescued from these pirates," Nuland said.

The rescue came amid escalating threats from Tehran, including assertions by Iran's army chief that American vessels are not welcome in the Gulf.

Iran's Foreign Minister Ali Akbar Salehi, however, played down the political significance of the rescue.

"On some occasions, Iran has helped and secured the released of many other countries' sailors that had been caught by pirates," he told state-run Press TV.

"This is a humanitarian gesture and it is not related to the countries' relations with each other."

Focus on Afghan border

Iran launched a military manoeuvre near its border with Afghanistan on Saturday, the semi-official Fars news agency reported, days after naval exercises in the Gulf increased tensions with the West and pushed up oil prices.

Mohammad Pakpour, commander of the Revolutionary Guards' ground forces, said the "Martyrs of Unity" exercises near Khvat, 60 km from Afghanistan, were "aimed at boosting security along the Iranian borders," Fars reported.

The Revolutionary Guards' naval forces' 10-day exercise in the Gulf that ended last Monday worsened relations with Washington days after US President Barack Obama approved sanctions that aim to stop countries buying Iranian oil.

Iran has also warned that it could block the Strait of Hormuz, the strategic waterway that carries to market much of the oil pumped in the Middle East.

The Iranian threats were in response to strong economic sanctions against Iran over its disputed nuclear enrichment program.

Source: Agencies