President Donald Trump has said the US Navy shot down an Iranian drone in the Strait of Hormuz.
He said the USS Boxer amphibious assault ship “took defensive action” on Thursday after the drone came within about 1,000 yards (914m) of the vessel.
Iran said it had no information about losing a drone. In June, Iran downed a US military drone in the area.
Earlier, Tehran said it had seized a “foreign tanker” and its 12 crew on Sunday for smuggling fuel in the Gulf.
Iran has been blamed by the US for attacks on tankers since May in the world’s key shipping area. Tehran denies all the accusations.
The recent incidents have triggered fears of a military conflict in the region.
What did President Trump say?
Speaking at the White House, he said: “I want to apprise everyone of an incident in the Strait of Hormuz today involving USS Boxer, a navy amphibious assault ship.
“The Boxer took defensive action against an Iranian drone which had closed into a very, very near distance, approximately 1000 yards, ignoring multiple calls to stand down and was threatening the safety of the ship and the ship’s crew. The drone was immediately destroyed.
“This is the latest of many provocative and hostile actions by Iran against vessels operating in international waters. The United States reserves the right to defend our personnel, facilities and interests.”
Washington earlier said Iran must immediately release the tanker it said it had seized.
Iran’s state media quoted Iran’s Revolutionary Guards as saying the vessel had been smuggling one million litres (220,000 gallons) of fuel.
The state media later published footage of Iranian speedboats circling around the Panamanian-flagged Riah tanker.
The tanker was seized south of Iran’s Larak Island, Iran said.
What’s the background to this?
Tensions have been high in the Gulf since the US tightened the sanctions that it reimposed on Iran’s oil sector after unilaterally withdrawing from a landmark 2015 nuclear deal.
The US has blamed Iran for two separate attacks on oil tankers in the Gulf of Oman in May and June – an allegation Tehran has denied.
Iran also shot down a US surveillance drone over the Strait of Hormuz. Tehran said the aircraft had violated Iranian airspace, and that the incident sent a “clear message to America”.
The US military said the drone had been over international waters at the time, and condemned what it called an “unprovoked attack”.
UK warships have meanwhile been shadowing British oil tankers in the area since Iran threatened to seize one in response to the impounding of an Iranian tanker off Gibraltar.
The UK said the tanker was suspected of breaching EU sanctions against Syria. Iran denied it was en route there.
US Central Command Chief General Kenneth McKenzie, speaking on a visit to Saudi Arabia on Thursday, said he was working “aggressively” to find a solution to free passage for ships through the Gulf region, Reuters news agency reports.