Boris Johnson has told Iran to “face up to the consequences” of its actions following an attack on an oil tanker in which a Briton was killed.
Foreign Secretary Dominic Raab has said it is highly likely that Iran was behind the drone strike on the MV Mercer Street off the coast of Oman.
The Prime Minister said Hassan Rouhani’s government should accept responsibility for the attack.
“I think that Iran should face up to the consequences of what they have done, accept the attribution that the Foreign Secretary has made,” Mr Johnson said.
“This was clearly an unacceptable and outrageous attack on commercial shipping, a UK national died.
“It is absolutely vital that Iran and every other country respects the freedoms of navigation around the world, and the UK will continue to insist on that.”
Iran’s ambassador to the UK Mohsen Baharvand was summoned to the Foreign Office on Monday and told by Middle East minister James Cleverly that Tehran must “immediately cease actions that risk international peace and security”.
The strike on the vessel last Thursday has been linked to tensions between Iran and Israel which have seen at least three other Israeli-linked ships targeted since February.
British maritime security firm Ambrey said the attack, which saw a hole blasted through the vessel’s bridge, killed one of its employees on board.
The Mercer Street is managed by London-based Zodiac Maritime, part of Israeli billionaire Eyal Ofer’s Zodiac Group.
The Foreign Office said the drone assault followed similar attacks on three other Israeli-linked ships in the region since February.
A Foreign Office spokesman said: “The Iranian ambassador to the UK, Mohsen Baharvand, was summoned today to the Foreign, Commonwealth & Development Office by the minister for the Middle East, James Cleverly, in response to the unlawful attack committed on MV Mercer Street on 29 July.
“Minister Cleverly reiterated that Iran must immediately cease actions that risk international peace and security, and reinforced that vessels must be allowed to navigate freely in accordance with international law.”
Mr Raab has promised to work with allies on a “concerted response” to Iran following the attack, which also killed a Romanian.
US Secretary of State Antony Blinken said he is confident that Iran carried out the attack using explosive drones – “a lethal capability it is increasingly employing throughout the region”.
Tehran has denied responsibility, accusing Israel of making baseless accusations against Iran.