Four Iranian boats harassed a U.S. destroyer in the Strait of Hormuz on Tuesday, prompting the American ship to sound its whistle and fire flares into the air.

A Navy official said the boats came within 300 yards of the destroyer off its side. While no shots were fired, the USS Nitze did have to alter its course to increase the distance between it and the Iranian boats.

The U.S. attempted to contact the Iranian sailors on the radio, but they did not answer, the official said.

It's not the first clash between the U.S. and Iran in the Strait. In January, the aircraft carrier Harry S. Truman reportedly came within about 1,500 yards of an Iranian rocket while the Iranian Revolutionary Guards Corps were conducting live-fire exercises. Officials called the test fire at such close proximity to the U.S. ship "unnecessarily provocative and unsafe."