In the latest dangerously close encounter between US and Iranian navies, Reuters reports that a U.S. Navy destroyer fired three warning shots at four of Iran's Islamic Revolutionary Guard Corps vessels on Sunday after they closed in at a high rate of speed in the Strait of Hormuz, according to two U.S. defense officials.

The Reuters sources said that the USS Mahan established radio communication with the boats but they did not respond to requests to slow down.

The Navy destroyer fired warning flares and a U.S. Navy helicopter also dropped a smoke float.

The Iranian vessels came within 900 yards (800 meters) of the Mahan, which was escorting two other U.S. ships.

The last such encounter in which a US navy ship fired warning shots at Iranian vessels took place last August, when the USS Nitze fired three warning shots after a "harassing" Iranian fast-attack craft approached and circled two U.S. Navy ships and a Kuwaiti vessel in the northern Gulf. The U.S. ship fired the shots into the water after the Iranian ship did not leave after a brief radio conversation.

The Iranian vessels had moved at high speed toward the Nitze, which allegedly was operating in accordance with international law in international waters and ignored maritime "rules of the road" as set out in the 1972 Convention on the International Regulations for Preventing Collisions at Sea. According to the Navy official, the IRGC vessels ignored multiple warnings, creating a dangerous, harassing environment that could have pushed the Nitze to take defensive measures, escalating the situation. At the time, Iran's defense minister insinuated that the incident occurred inside Iranian territory.