WASHINGTON (CNN) -- A U.S.-contracted cargo ship fired warning shots in the Persian Gulf at two small patrol boats believed to be from Iran, U.S. Navy officials said Friday.

The crew of the Westward Venture, which was under contract to the U.S. government, reported that it radioed a warning and fired flares before resorting to warning shots Thursday, the officials said.

The ship carried a Navy mobile security team that is authorized to respond to perceived threats, as do all military-contracted ships in the 5th Fleet's area of command in the waters surrounding the turbulent Middle East and East Africa, the Navy said.

The cargo vessel was en route to Kuwait and about 50 miles from the Iranian coast, according the reports.

The Revolutionary Guard, part of Iran's military, says no such incident took place, according to the state-run Islamic Republic News Agency.

Tensions in the Persian Gulf have been high this year. The United States and Iran, which have no diplomatic relations and blame each other for problems in Iraq, have had at least two other tense incidents in the Gulf since January.

This month, the U.S. military reported that three small Iranian boats approached the patrol ship USS Typhoon in a "taunting manner." Two of the boats turned away, but one came within 200 yards of the Typhoon, prompting a crew member to fire a warning flare.

Through its state-run news agency, Iran denied reports of the April 10 incident, saying the U.S. media "tries to portray the Persian Gulf as a turbulent area in order to prepare the grounds for the permanent presence of U.S. forces in the region."

On January 6, five boats belonging to Iran's Revolutionary Guard "harassed and provoked" three U.S. Navy ships in the Strait of Hormuz, a narrow shipping channel leading into and out of the Persian Gulf, the U.S. military said.

Though the United States deemed the encounter "significant," an Iranian official told Iran's state-run media that it was not a serious incident. E-mail to a friend

CNN's Shirzad Bozorgmehr contributed to this report.

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