This Jan. 2, 2016 photo shows the Liberian-flagged oil tanker Mercer Street off Cape Town, South Africa. Credit: Johan Victor via AP

The U.S. formally blamed Iran for a deadly attack on an Israel-linked oil tanker off Oman, warning of an “appropriate response.”

“There is no justification for this attack, which follows a pattern of attacks and other belligerent behavior,” Secretary of State Antony Blinken said in a statement Sunday. “We are working with our partners to consider our next steps and consulting with governments inside the region and beyond on an appropriate response, which will be forthcoming.”

Blinken’s condemnation came after Israeli Prime Minister Naftali Bennett said Iran was “unequivocally” responsible for the attack on Thursday. The U.K. foreign secretary issued a similar condemnation. None of the statements offered direct evidence.

“We expect the international community to clarify to the Iranian regime that it made a terrible mistake,” Bennett said. “We have our ways of getting the message to Iran.”

Two crew members — a Romanian and a Briton — died aboard the Mercer Street, the first fatalities in years in the volatile shipping corridor. Earlier on Sunday, Iran denied responsibility.

“Israel should stop leveling such accusations against Iran,” a spokesman for the Iranian foreign ministry, Saeed Khatibzadeh, said in a press briefing in Tehran on Sunday. “It’s not the first time that Israel is making such accusations.”

U.S. Navy experts on Saturday said they believe the oil products tanker was struck by a drone. In his statement U.K. Foreign Secretary Dominic Raab said “one or more” drones may have been involved.

Raab said “this attack was deliberate, targeted, and a clear violation of international law by Iran.”

Iran and Israel have traded multiple accusations of shipping attacks in recent months. They’ve happened amid efforts by world powers to restore a 2015 pact that limited Tehran’s nuclear activities in return for an easing of U.S. sanctions. Israel is against a lifting of sanctions or a revival of the deal.

The 600-foot tanker was sailing, empty of cargo, from Tanzania’s Dar es Salam to Fujairah in the United Arab Emirates, said London-based Zodiac Maritime Ltd., manager of the vessel.

Zodiac is controlled by real estate and shipping magnate Eyal Ofer and operates the Japanese-owned carrier. Ofer is among Israel’s richest people, with a net worth of $11.3 billion, according to the Bloomberg Billionaires Index.

Story by Arsalan Shahla.