Washington, Jul 26 (IANS): A US Navy vessel fired warning shots at an Iranian patrol boat in the waters of the northern Persian Gulf, US Defence Department officials said.

According to the sources, the Iranian boat, apparently belonging to that country's Revolutionary Guard, approached within about 140 m of the USS Thunderbolt, which reacted by firing warning shots, Efe news reported.

Two Defence Department officials told CNN that the Thunderbolt, based in Bahrain as part of the US 5th Fleet, was sailing in international waters along with three other US vessels: the missile cruiser USS Vella Gulf and two Coast Guard boats.

The Thunderbolt was engaged in a routine patrol in the Gulf when the incident occurred, US officials said.

The Thunderbolt fired warning shots because the Iranian boat did not respond to several warnings -- sent via radio and using flares -- of a possible collision if it were to have continued on its initial course.

US and Iranian warships have been involved in a number of naval incidents in the Persian Gulf over the past few years.

According to the US Navy, a total of 35 incidents considered to be "unsafe and/or unprofessional" involving Iranian vessels took place in 2016, up from 23 registered in 2015.

Iranian forces view the presence of US ships in the Persian Gulf as a provocation and have also accused the US Navy of "unprofessional" behaviour.