text: Iran's Revolutionary Guards 'harassed' a US-flagged commercial ship just days before it seized a vessel carrying cargo and 34 sailors, it has emerged. The two incidents have raised concerns about the security of shipping lanes in the strategic Strait of Hormuz, Pentagon spokesman Colonel Steven Warren said. News of the first incident was revealed by the Pentagon after Iranian guards seized MV Maersk Tigris this week, by firing warning shots across the vessel's bows. ranian patrol vessels fired warning shots across the bridge of the Marshall Islands-flagged cargo vessel the Maersk Tigris Tuesday morning and seized it for trespassing just days after it had 'harassed' another ship . In the April 24 incident, four Iranian patrol boats with the country's elite Revolutionary Guards 'harassed a US-flagged merchant ship called the Maersk Kensington' as it moved along an established shipping route, said Mr Warren. The Iranian vessels 'followed her for approximately 15 to 20 minutes in actions the ship master of the Kensington interpreted as aggressive,' he said. The American military was not involved in the incident and the Kensington's captain later filed a report with the US Navy describing the event. Just four days later, Iranian boats forced a Marshall Islands-flagged ship, the Maersk Tigris, to Iran's Larak Island after firing warning shots across the bows and boarding the vessel. Iran has said it seized control of the container ship due to a commercial dispute with Denmark's giant Maersk group, which chartered the vessel to ferry cargo in the region. When it was intercepted, the Tigris was traveling on an international shipping route within Iran's territorial waters. 'It's difficult to know exactly why the Iranians are behaving this way,' Warren said. 'We call on them to respect all of the internationally established rules of freedom of navigation, the law of the sea to which they are a signatory and other established protocols,' he said. The 52,600-ton container ship was built in 2014 and is managed by Singapore-based Rickmers Ship Management . Iranian sources have seized the cargo ship and claim they had a legal order following a dispute . In a statement, the Iranian Port and Maritime Organisation said the Maersk Tigris was intercepted 'upon a legal order' and transferred to Shahid Bahonar port in southern Iran. Officials claimed the order was issued following a 'long running commercial dispute' with Maersk. The ruling was 'based on a lawsuit by a private company called Pars Talayieh Oil Product company (Golden Pars Oil Products) against Maersk ship company,' it said. They said the ship can only be released following a judicial ruling. Iran's Foreign Minister Mohammad Javad Zarif, speaking at New York University, said a lawsuit was filed against the ship's owners between 15 and 16 years ago over an undelivered cargo. 'It has gone through court proceedings in Tehran based on what I hear from the lawyer. The final decision by the court is that the ship's owners are supposed to pay damages,' he said. Saudi-owned Al Arabiya television station reported earlier the vessel was US-flagged, but it has since emerged that the cargo ship is registered in the Pacific island nation and had no Americans aboard. The semi-official Iranian news agency Fars also reported that Iran took control of the MV Maersk Tigris for 'trespassing' on its territorial waters. Warren said the cargo ship's master had initially refused an Iranian order to move further into Iranian waters, but after the warning shots were fired the cargo ship complied. The vessel was then boarded by Iranians, but no one has been injured and no Americans are involved. Detained: A map of the vessel's route shows that it abruptly changed course in the Strait of Hormuz this morning and was heading to the Iranian port on Bandfar Abbas . Warren said the cargo ship issued a distress call and US Naval Forces Central Command, based in the area, sent a US destroyer, the USS Farragut, and a P-3 surveillance aircraft to the area of the incident to monitor the situation. 'What they are doing is keeping an eye on things. They are in close enough proximity to the Maersk Tigris that they will be able to respond if a response is required,' he added. As the US government had defense and other ties with the Marshall Islands, US officials were 'in discussion with the Marshall Islands on the way ahead,' he said. 'The Republic of Marshall Islands has requested assistance for the release of the Maersk ship, and again, we're in communication with them about how best to expect that outcome,' State Department spokeswoman Marie Harf said. But US officials said privately that no military action was imminent. According to the ship-tracking site MarineTraffic.com, the 52,600-ton cargo vessel, which was built last year, departed from Ambarli, Turkey April 8 en route to Jebel Ali in the United Arab Emirates. Peacekeeper: A US destroyer, the USS Farragut (pictured), and an aircraft to the area of the incident to monitor the situation . A map of the vessel's route shows that it abruptly changed course in the Strait of Hormuz this morning and was heading to the Iranian port of Bandar Abbas. New of the seizure and action against another vessel comes amid heightened tensions in the Gulf, fuelled by the Yemen conflict and high-stakes diplomacy between Washington and Tehran over Iran's nuclear program. In October 2012, Maersk announced a halt to its activities in Iran after Western oil and financial sanctions were slapped on the country over its controversial nuclear program. The ship was operated by Rickmers Ship Management, with head offices in Singapore and Hamburg, and was carrying cargo for Maersk Line, the group's shipping unit which had chartered the vessel. A spokesman for the Danish group said the Maersk Tigris does not belong to the company and it does not employ the crew. The shipping group A.P. Moeller-Maersk also said Wednesday that the crew was safe but it remained tight-lipped about any commercial dispute.
target: Iran Revolutionary Guards seized MV Maersk Tigris with 34 sailors aboard .
  Iranian navy harassed another Maersk ship days before, Pentagon said .
  Revelations have raised concerns about the security of shipping lanes .
  Officials from Iran claimed they seized Maersk Tigris under a legal order following a long running legal dispute with the shipping company .