The US on August 2 promised to lead a “collective response” against Iran in retaliation for a deadly attack on an Israeli-linked tanker, as Tehran denied blame and warned against “adventurism”.

The US and Israel have both said that their intelligence concluded that an Iranian drone on July 29 attacked the MT Mercer Street, managed by prominent Israeli billionaire Eyal Ofer, as it sailed off Oman.

A British security guard and a Romanian crew member were killed in what analysts said bore all the hallmarks of the “shadow war” between enemies Iran and Israel, which have included attacks in waters around the Gulf.

Top US diplomat Antony Blinken called the Mercer Street incident “a direct threat to freedom of navigation and commerce”.

“We are in very close contact, in coordination, with the United Kingdom, Israel, Romania and other countries. And there will be a collective response,” Blinken told reporters, the second straight day he has threatened retaliation.

Britain summoned the Iranian ambassador and demanded that vessels navigate freely in the oil-rich region.

“I think that Iran should face up to the consequences of what they’ve done,” British Prime Minister Boris Johnson told reporters, condemning the “unacceptable and outrageous attack” on the ship.

Iranian foreign ministry spokesman Saeed Khatibzadeh said Israel “must stop such baseless accusations” and called on the US and Britain to provide evidence if any to support claims of Tehran’s responsibility.

Iran “will not hesitate to protect its security and national interests, and will immediately and decisively respond to any possible adventurism”, Khatibzadeh said in a statement.

Iran’s foreign ministry also summoned the British charge d’affaires and Romanian ambassador to object to the “baseless” allegations over the ship, the state-run Islamic Republic News Agency (Irna) said.

The incident came ahead of August 3’s inauguration of the ultraconservative Ebrahim Raisi as Iran’s new president, replacing Hassan Rouhani who had tried to improve relations with the West.

Israel, which sees Iran as its primary adversary, has gone on the offensive against the clerical state including through air strikes in war-ravaged Syria, where Tehran has been a top backer of President Bashar al-Assad.

Al-Alam, an Arabic-language network run by Iran, cited sources as saying that the Mercer Street incident was a response to an Israeli strike on an airport in Syria but offered no details.

Israeli defence minister Benny Gantz said the ship incident amounted to an “escalation” by Iran.

“This is exactly the reason we must act now against Iran, which is not just moving toward a nuclear weapon but also is bringing about a dangerous arms race,” Gantz told parliament.

He said Iranian-linked militia groups will soon have “hundreds” of Iranian-built drones including in Yemen and Iraq.