G7 foreign ministers said Friday that Iran was behind the deadly July 29-30 attack on a tanker, while the US military released details of the explosive drone and said it was produced in Iran.
Meanwhile, the UN Security Council agreed to discuss the incident off the coast of Oman on Monday as pressure mounted on Tehran.
"All available evidence clearly points to Iran" in the attack on the Israel-linked tanker that killed a former British soldier and a Romanian national, the G7 said in a statement.
"This was a deliberate and targeted attack, and a clear violation of international law... There is no justification for this attack," the ministers from the seven developed nations said in a statement.
Iran has strongly denied having any link to the attack on the M/T Mercer Street, which came as tensions grow in the region and with talks to revive the 2015 deal on the Iranian nuclear program at a standstill.
The G7 ministers said "vessels must be allowed to navigate freely in accordance with international law," and vowed to "do our utmost to protect all shipping, upon which the global economy depends."
"Iran's behaviour, alongside its support to proxy forces and non-state armed actors, threatens international peace and security," they said, calling on Tehran to stop all activities inconsistent with UN Security Council resolutions.
European countries and the United States renewed their accusations at a closed-door Security Council meeting at the UN headquarters in New York Friday.
"The UK knows that Iran was responsible for this attack. We know it was deliberate and targeted," said British Ambassador to the UN Barbara Woodward, who added the evidence was "clear cut."
"The door for diplomacy and dialogue remains open. But if Iran chooses not to take that route, then we would seek to hold Iran to account and apply a cost to that," she told reporters.
The UN Security Council is due to discuss the incident further at an open meeting on maritime security on Monday.
'Produced in Iran'
Meanwhile, the US Central Command, which operates in the Middle East, released the results of its initial investigation and said the remnants of the drone indicated it was made in Iran.
CentCom said three one-way drones laden with explosives were targeted in the attack, but the first two failed to strike the ship and plunged into the sea.
Remnants of one of those were retrieved by investigators.
The third drone struck the ship, exploding and leaving a six-foot (two-meter) hole on the ceiling of the bridge.
CentCom said the drone had been packed with the explosive RDX, and pieces recovered from it "were nearly identical to previously-collected examples from Iranian one-way attack UAVs," or unmanned aerial vehicles.
"US experts concluded based on the evidence that this UAV was produced in Iran," they said.
CentCom did not say where the drones were launched from, but said: "The distance from the Iranian coast to the locations of the attacks was within the range of documented Iranian one-way attack UAVs."
The Mercer Street is an oil products tanker operated by Israeli-controlled Zodiac Maritime.
The Pentagon said US Defense Secretary Lloyd Austin spoke Friday with Israeli Defense Minister Benny Gantz about the incident.
Both "expressed concern about Iran's proliferation and employment of one-way attack UAVs across the region and committed to continue cooperating closely on regional security," the Pentagon said in a statement.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)