The US secretary of state, Mike Pompeo, has been urged by European leaders to show maximum restraint towards Iran after Saudi Arabia confirmed that two of its vessels had been mysteriously sabotaged on Sunday in the waters off Oman by an unidentified assailant.

Federica Mogherini, the EU’s foreign affairs chief, warned Pompeo in a hastily arranged meeting in Brussels: “We are living in crucial delicate moments where the most responsible attitude to take and should be is maximum restraint and avoiding any escalation on the military side.”

Tensions have been spiralling for weeks as the US adopts a policy of maximum pressure on Iran, including ending all waivers for Iranian oil exports and blocking cooperation on Iran’s civil nuclear programme. It has sent an aircraft carrier to the region, but the US special representative on Iran, Brian Hook, declined to say if Iran was responsible for the attack on the Saudi oil ships.

The British foreign secretary, Jeremy Hunt, warned of a conflict erupting in the Gulf by accident and called for calm.

But Iran, frustrated at the EU’s inability to protect the Iranian economy, responded to the cumulative US pressure last Wednesday by saying it was preparing initial steps to distance itself from the nuclear deal it signed with the EU, the US, China and Russia.

Donald Trump pulled the US out of the deal a year ago, saying it was one-sided and would put Iran on the path to becoming a nuclear weapon state.

Mogherini urged maximum restraint, as an explicit counterpoint to the US call for maximum pressure, at a press conference in Brussels following a meeting with EU foreign ministers. She did nothing to disguise her differences with the US, repeating that the UN’s IAEA energy watchdog was the only body capable of declaring if Iran was in breach of the deal.

Mogherini refused to commit Europe to taking as much as 1.5m barrels per day of Iranian oil, but insisted the EU was determined to “use all its instruments to implement the nuclear deal in full”. She hoped the first transactions would take place in the next few weeks under the instrument in support of trade and exchanges (Instex) a complex system designed to facilitate trade with Iran without recourse to banks. The system is seen by Tehran as a litmus test of European willingness to boost the Iranian economy.

Pompeo’s aides said the secretary of state gave intelligence in Brussels on how Iran was seeking to disrupt US assets across the Middle East.

Asked on Monday about US intelligence and intentions in the region, Trump told reporters in Washington: “I’m hearing little stories about Iran. If they do anything, they will suffer greatly. We’ll see what happens with Iran.”

The United Arab Emirates said on Sunday that four commercial vessels had been sabotaged near Fujairah emirate, outside the Strait of Hormuz. The UAE did not give details of the ships’ nationalities or ownership, but Riyadh identified two of them as Saudi and a Norwegian company said it owned another. The fourth ship was reportedly the A Michel, a storage tanker flagged in Sharjah, one of the UAE’s seven emirates.

Shipping industry sources identified the Saudi vessels as the large crude carrier tanker Amjad and crude tanker Al Marzoqah, owned by Bahri, Saudi’s national shipping carrier, which has yet to comment.

No country has taken responsibility for the alleged acts of sabotage. Iran called for an investigation into the incident and spoke of “adventurism” by foreign players to disrupt maritime security.

The Saudi energy minister, Khalid al-Falih, said the incident involving the two Saudi-owned vessels occurred on Sunday at 6am. Riyadh has yet to produce photographic evidence of damage.

Thome Ship Management said its Norwegian-registered oil products tanker MT Andrew Victory was “struck by an unknown object”. Footage seen by Reuters showed a hole in the hull at the waterline with the metal torn open inwards.

The cause of the damage and type of weapon used remains a mystery. If the cause was a device in the water, the only reported and comparable use of such devices in the region recently has been the deployment by Houthi rebels of naval mines, several dozen of which have been deployed in the conflict in Yemen, including at least one improvised device.

Houthis have also targeted Saudi oil facilities with missiles in the past, including four missiles fired at the Saudi Aramco facilities on the Red Sea last year.

A Saudi government source said: “This criminal act constitutes a serious threat to the security and safety of maritime navigation and adversely impacts regional and international peace and security.”

Falih said one of the two Saudi vessels was on its way to be loaded with Saudi crude oil from the port of Ras Tanura, to be delivered to Saudi Aramco’s customers in the US. “Fortunately, the attack didn’t lead to any casualties or oil spill; however, it caused significant damage to the structures of the two vessels,” he said.

Fujairah port is the only Emirati terminal located on the Arabian Sea coast, bypassing the Strait of Hormuz, through which most Gulf oil exports pass. Almost all oil exports of Saudi Arabia, Iraq, the UAE, Kuwait, Qatar and Iran itself – at least 15m barrels per day – are shipped through the strait. The world’s largest crude oil storage centre is also being built in Fujairah.

Iran has repeatedly threatened to close the strait in the case of a military confrontation with the US.

Additional reporting by Peter Beaumont and Rob Davies