WASHINGTON—Four ships from Iran's Revolutionary Guard Corps harassed a U.S. destroyer near the Persian Gulf in what the U.S. Navy called an "unsafe and unprofessional" interaction.

The USS Nitze, an Arleigh-Burke class guided-missile destroyer, was transiting international waters near the Strait of Hormuz on Tuesday when the four Iranian vessels approached at high speed and failed to respond to 12 separate radio communications, according to Cdr. William Urban, a spokesman for the U.S. Fifth Fleet.

The USS Nitze blew its whistle in five short blasts on three occasions—signaling the Iranian vessels were on a dangerous course—and fired off 10 flares in the direction of the approaching ships before altering course to avoid a potential collision, Cmdr. Urban said.

As two of the Iranian vessels came within 300 yards of the destroyer, the quartet finally slowed speed and motored away from the U.S. ship, according to Cmdr. Urban, who characterized the interaction as a dangerous, harassing situation that could have led to further escalation. The USS Nitze was transiting the waters with the USS Mason, another guided-missile destroyer.

The incident was one of many interactions between Iranian and American ships in and around the Persian Gulf in recent months. But it was one of few the U.S. Navy has deemed unsafe or unprofessional.

According to a U.S. defense official, the Navy deemed about 10% of the hundreds of interactions between Iranian and American ships unsafe or unprofessional in 2015 and the first half of 2016. The official said the number of interactions—both safe and unsafe—has increased this year compared with 2015.

Iranian officials couldn't immediately be reached for comment.

Write to Paul Sonne at paul.sonne@wsj.com

(END) Dow Jones Newswires

August 24, 2016 20:35 ET (00:35 GMT)