A US coastguard ship accompanying a guided-missile submarine and other vessels near the Strait of Hormuz fired warning shots at Iranian fast boats that approached in an “unsafe” manner on Monday, the Pentagon’s spokesman said.
A large group of fast boats from the Islamic Revolutionary Guard Corps came as close as 140 metres to the US ships when a coastguard cutter fired about 30 warning shots from a .50-calibre machinegun, spokesman John Kirby said.
Mr Kirby said the Iranian vessels were being driven “very aggressively".
The encounter is the latest sign of US-Iran tension and the second time an American boat has fired at an Iranian vessel in recent weeks.
Late last month, the US released footage of the USS Firebolt firing on Iranian fast boats that came within about 60 metres.
In early April, an Iranian boat pulled in front of another coastguard vessel, although no shots were fired.
“It’s unsafe, it’s unprofessional and this is the kind of activity that could lead to somebody getting hurt and could lead to a real miscalculation in the region,” Mr Kirby said.
“Sadly, harassment by the IRGC Navy is not a new phenomenon.”
The US ships were entering the Arabian Gulf when they were approached, Mr Kirby said.
The encounters come despite US and Iranian negotiators taking part in indirect talks in Vienna over how to revive the 2015 nuclear agreement between Tehran and world powers.