WASHINGTON, April 27 (Xinhua) -- A U.S. Navy patrol ship fired warning shots at Iranian Islamic Revolutionary Guard Corps Navy (IRGCN) vessels in international waters of the northern Persian Gulf, the Navy said on Tuesday.

Three IRGCN armed speed boats Monday rapidly approached U.S. Navy patrol coastal ship USS Firebolt and a U.S. Coast Guard patrol boat to "unnecessarily close range with unknown intent, including a closest point of approach of 68 yards (62 meters) to both U.S. ships," the Navy said in a statement.

"The U.S. crews issued multiple warnings via bridge-to-bridge radio and loud-hailer devices, but the IRGCN vessels continued their close range maneuvers," the statement said. "The crew of Firebolt then fired warning shots, and the IRGCN vessels moved away to a safe distance from the U.S. vessels."

U.S. media reported that it was the first time the U.S. Navy had fired on Iranian vessels in nearly four years.

The incident also came amid indirect talks between the United States and Iran in Vienna to revive the Iran nuclear deal, formally known as the Joint Comprehensive Plan of Action (JCPOA).

Iran gradually stopped implementing parts of its commitments under the JCPOA in May 2019, one year after former U.S. President Donald Trump unilaterally abandoned the agreement and re-imposed sanctions on Iran.