Two commercial oil tankers carrying inflammable materials caught fire in suspected attacks on Thursday in the Gulf of Oman, AFP reported. Dozens of crew members were evacuated off the coast of Iran.

The incident drove up oil prices and stoked fears of a new confrontation between Iran and the United States. In May, Washington had accused Tehran of being behind a similar incident when four tankers were damaged in the same area.

Iran said its navy rescued 44 crew members after the two vessels caught fire in “accidents” off its coast. Twenty one crew members were on board the Singapore-owned Kokuka Courageous and the 23 were on Norwegian-owned tanker Front Altair.

However, the United States disputed this, saying its Navy had rescued some of those aboard. “US naval forces in the region received two separate distress calls at 6:12 am local time and a second one at 7:00 am,” the US Fifth Fleet said.

The Norwegian Maritime Authority said three explosions were reported on Front Altair after it was attacked along with Kokuka Courageous. Iran state media said the first incident occurred on board the Front Altair at 8:50 am (0420 GMT) 25 nautical miles off Bandar-e-Jask in southern Iran.

Iran’s Foreign Minister Mohammad Javad Zarif described Thursday’s incidents as suspicious on Twitter, noting they occurred during Japanese Prime Minister Shinzo Abe’s Tehran visit. The minister called for regional dialogue. “Suspicious doesn’t begin to describe what likely transpired this morning. Iran’s proposed Regional Dialogue Forum is imperative,” Zarif said on Twitter.

Britain said it was “deeply concerned” about the attacks. Germany, which like Britain remains a signatory to the nuclear pact with Iran, said the “situation is dangerous” and all sides needed to avoid an escalation.

United Nations chief condemns tanker attacks

United Nations Secretary-General Antonio Guterres said he strongly condemned any attack against civilian vessels. The world cannot afford a major confrontation in the Gulf, Guterres warned. “Facts must be established and responsibilities clarified,” he said. “If there is something the world cannot afford, it is a major confrontation in the Gulf region.”

On May 12, four oil tankers – two Saudi, one Norwegian and one Emirati – were damaged in still unexplained attacks in the Gulf of Oman off the United Arab Emirates.

The attacks also come in the backdrop of an escalating standoff between the US and Iran one year after President Donald Trump withdrew from the 2015 Iran nuclear deal and reimposed heavy sanctions on the country. Iran responded to the sanctions by threatening to walk away from its obligations under the nuclear deal – which had promised economic relief in exchange for limits to its nuclear development – and return to higher levels of uranium enrichment.