US Navy explosive experts believe a “drone strike” targeted an oil tanker that came under attack off the coast of Oman in the Arabian Sea, killing two on board, the American military said Saturday.

The strike Thursday night on the oil tanker Mercer Street marks the first-known fatal attack after years of assaults on commercial shipping in the region linked to tensions with Iran over its tattered nuclear deal. While no one has claimed responsibility for the attack, Israeli officials alleged Tehran launched the drone strike.

While Iran did not directly acknowledge the attack, the strike comes as Tehran now appears poised to take an even tougher approach with the West as the country prepares to inaugurate a hard-line protégé of Supreme Leader Ayatollah Ali Khamenei as president.

The American nuclear-powered aircraft carrier USS Ronald Reagan and the guided missile destroyer USS Mitscher were escorting the Mercer Street as it headed to a safe port, the US Navy’s Mideast-based 5th Fleet said in a statement early Saturday.

Israeli Foreign Minister Yair Lapid tweeted late Friday that he spoke with British Foreign Secretary Dominic Raab about the “need to respond severely” to the attack, although he stopped short of directly blaming Iran.

“Iran is not just an Israeli problem, but an exporter of terrorism, destruction and instability that affects the whole world,” Lapid wrote. “We can never remain silent in the face of Iranian terrorism, which also harms freedom of navigation.”

Other Israel-linked ships have been targeted in recent months as well amid a shadow war between the two nations, with Israeli officials blaming the Islamic Republic for the assaults.

Israel meanwhile has been suspected in a series of major attacks targeting Iran’s nuclear program. Also, Iran saw its largest warship recently sink under mysterious circumstances in the nearby Gulf of Oman.

Thursday’s attack comes amid heightened tensions over Iran’s tattered nuclear deal and as negotiations over restoring the accord have stalled in Vienna.

The series of ship attacks suspected to have been carried out by Iran began a year after then-President Donald Trump unilaterally withdrew America from the accord in 2018.

The attack on the Mercer Street also came the night after US Secretary of State Antony Blinken, speaking from Kuwait, warned Iran that talks in Vienna over the nuclear deal “cannot go on indefinitely.”

This is the second time this month a ship tied to Ofer apparently has been targeted. In early July, the Liberian-flagged container ship CSAV Tyndall, once tied to Zodiac Maritime, suffered an unexplained explosion on board while in the northern Indian Ocean, according to the US Maritime Administration.