Two commercial oil tankers were hit by explosions and caught fire in the Gulf of Oman, prompting the evacuation and rescue of dozens of crew members. The United States blamed Iran, accusing it of trying to disrupt oil supplies through the strategic waterway.
Ship operators said that 21 crew members on board the Japanese-owned Kokuka Courageous tanker and 23 on the Front Altair, owned by Norway, were evacuated by nearby vessels after the blasts on June 13.
Iranian state media reported that the Iranian Navy rescued the 44 and transferred them to an Iranian port, a claim disputed by the United States, which said its navy had come to the rescue of some of those aboard the ships.
One crewman was said to have been slightly injured.
The incidents come a month after attacks on four tankers off the nearby United Arab Emirates increased tensions between Tehran and Washington and U.S. allies in the Persian Gulf.
In Washington, U.S. Secretary of State Mike Pompeo blamed Tehran, citing the type of explosives used and what he said was the sophistication of the attacks. He asserted it was part of a campaign to escalate tensions in the region.
"This is only the latest in a series of attacks, instigated by the Islamic Republic of Iran and its surrogates, against the United States and its allies," Pompeo said. "And they should be understood in the context of 40 years of unprovoked aggression against freedom-loving nations."
Earlier at the United Nations Security Council, the U.S. ambassador condemned the attacks and added that Washington was providing assistance.
"It's unacceptable for any party to attack commercial shipping and today's attacks on ships in the Gulf of Oman raise very serious concerns," the U.S. envoy, Jonathan Cohen, said.
UN Secretary-General Antonio Guterres warned at the meeting that the world cannot afford "a major confrontation in the Gulf region."
"I strongly condemn any attack against civilian vessels. Facts must be established and responsibilities clarified," Guterres said.
The Japanese government said the tankers carried "Japan-related" cargo.
The explosions came as Japanese Prime Minister Shinzo Abe wrapped up a two-day landmark visit to Tehran.
Iran's foreign minister described the incidents as suspicious, saying they occurred while Abe was meeting with Supreme Leader Ayatollah Ali Khamenei for "extensive and friendly talks."
"Suspicious doesn't begin to describe what likely transpired this morning,” Mohammad Javad Zarif said in a post to Twitter.
The Seafarers Union of Russia said there were 12 Russians among those evacuated, according to the Interfax news agency. The RIA Novosti news agency reported that all of the Russians rescued were safe and had not been injured.
The U.S. Navy's Bahrain-based Fifth Fleet earlier said it had received two distress calls, adding that U.S. ships were assisting.
The United Kingdom Maritime Trade Operations, a maritime safety group run by the British Navy, urged "extreme caution" in the area.
International Tanker Management, the firm that operates the Front Altair, said an explosion caused a fire on board the vessel, which was heading to the Far East with a petroleum product known as naptha.
Another shipping firm, BSM Ship Management, said an "incident” on board the Kokuka Courageous damaged the ship's hull on the starboard side. The vessel was carrying methanol.
Iran's IRIB news agency tweeted images of what it said was the ablaze Front Altair.
Tehran has been locked in a standoff with Washington since the United States one year ago pulled out of a landmark 2015 nuclear agreement between world powers and Iran.
Since then, Washington has reimposed crippling sanctions on Iran, stepped up its rhetoric, and beefed up its military presence in the Middle East, raising fears of a possible armed conflict. A U.S. aircraft carrier battle group arrived in the region last month.
The U.A.E. blamed last month's attacks just outside the Strait of Hormuz, a vital shipping route for global oil and gas supplies, on an unnamed "state actor," while the United States alleged that Iran used mines to attack the four tankers -- an accusation Tehran denied.
"Some parties in the region are trying to instigate fires in the region and we must be aware of that," Arab League Secretary-General Ahmed Aboul Gheit told the Security Council, without specifically naming anyone.
Kuwait's Foreign Minister Sheikh Sabah Khaled al-Sabah said the incidents were threatening international security.
In Moscow, Deputy Foreign Minister Sergei Ryabkov warned against drawing quick conclusions on the blasts.
"Measures to normalize the situation around Iran are needed. We need to be calm and unbiased when investigating what happened, avoid rash conclusions that can turn up the pressure cooker," Ryabkov said.
During his talks with the Japanese prime minister, Khamenei ruled out any negotiations with the United States.
"Iran does not trust the U.S.," Iran’s state media quoted Khamenei as saying. "We have already had the bitter experience with the Americans over the nuclear deal and do not want to repeat this experience."
Abe, the first sitting Japanese prime minister to visit Iran in more than 40 years, warned on June 12 that an "accidental conflict" should be avoided at all costs.
U.S. President Donald Trump responded to news of Abe's trip, saying he appreciated the visit but he thought it was "too soon to even think about" the United States making a deal with Tehran.
"They are not ready, and neither are we!" Trump said in a post to Twitter.