A US Coast Guard ship fired about 30 warning shots after 13 boats belonging to the Iranian Revolutionary Guard came close to it and other US naval vessels in the Strait of Hormuz, the US Department of Defense said on Monday. The incident marked the second time within the last month that US military vessels have had to fire warning shots because of what they said was unsafe behavior by Iranian vessels in the region, after a relative lull in such interactions over the past year. Pentagon spokesman John Kirby said the warning shots were fired after the Iranian vessels came as close as 150 yards (450 feet) of six US vessels. The US Coast Guard cutter Maui fired the warning shots from a .50-caliber machine gun before the Iranian vessels left, Kirby said. "It's significant... and they were acting very aggressively," he said, adding that the number of Iranian vessels was more than in the recent past. — Agencies