Britain on Monday summoned Iran's ambassador to London in response to what it claims was a Tehran-ordered attack on a merchant vessel off the coast of Oman that killed a British and Romanian national.
"The Iranian ambassador to the UK, Mohsen Baharvand, was summoned today to the Foreign, Commonwealth & Development Office... in response to the unlawful attack committed on MV Mercer Street on 29 July," said a British government statement.
"Iran must immediately cease actions that risk international peace and security," it added, saying that "vessels must be allowed to navigate freely in accordance with international law".
Foreign Secretary Dominic Raab on Sunday said that Britain "believes the attack... was carried out by Iran and was deliberate, targeted and unlawful".
Two crew members of the Japanese-owned, Liberian-flagged oil tanker, which is managed by a prominent Israeli businessman's company, were killed in what appeared to be a drone attack, the vessel's London-based operator and the US military said Friday. Israel also blamed Iran.
US Navy forces came to the aid of the crew in response to an emergency distress call and saw evidence of the attack, said a US military statement.
Analysts said the attack bore all the hallmarks of tit-for-tat exchanges in the "shadow war" between Israel and Iran, in which vessels linked to each nation have been targeted in waters around the Gulf.
Zodiac Maritime, owned by Israeli billionaire Eyal Ofer, said the incident on board the MT Mercer Street on Thursday killed one Romanian and a UK national, who was a guard for British maritime security firm Ambrey.
The vessel was in the northern Indian Ocean, travelling from Dar es Salaam in Tanzania to Fujairah in the United Arab Emirates with no cargo onboard when the attack occurred, it said.
Iran's state TV channel in Arabic Al-Alam, citing "informed regional sources", said the attack was a "response to a recent Israeli attack" targeting an airport in central Syria. It did not provide further details.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
Track Latest News Live on NDTV.com and get news updates from India and around the world