Oman’s foreign minister made a surprise visit to Iran on Monday, amid heightened tensions between the US, Saudi Arabia and the Islamic Republic.

Yusuf bin Alawi met with his Iranian counterpart in Tehran to discuss regional and international issues, the official IRNA news agency reported, without providing further details.

Oman has long served as a mediator in the region and has conciliated between Washington and Tehran on some occasions in the past, including during the early stages of the talks that led to the 2015 nuclear agreement.

The surprise visit comes amid soaring tensions in the region between Iran and the United States.

The stand-off had been simmering since the United States last year withdrew from the 2015 nuclear treaty which Iran reached with major world powers. The Trump administration also imposed sweeping US sanctions on Iran.

In recent days the US accused Iran of alleged threats and last week deployed an aircraft carrier group and B-52 bombers to the Gulf.

Iran had not made any direct public threats to spark the US deployment, but Washington says it acted on intelligence reports of Iranian actions.

Iran’s Foreign Minister Mohammad Javad Zarif criticised President Donald Trump on Monday for his overnight tweet threatening the Islamic Republic with its “official end“, saying Trump had been “goaded” into “genocidal taunts”.

Meanwhile on Monday, Yemen’s Iran-backed Houthi rebels have been accused of firing two missiles into Saudi Arabia, although the rebel group has denied the reports. A Saudi-owned satellite news channel reported that two missile were intercepted over the city of Taif and the Red Sea port of Jeddah.

As US-Iran tensions escalate, there’ve been concerns that Iraq could once again get caught in the middle. A rocket was fired into the Iraqi capital’s heavily fortified Green Zone on Monday, landing less than a mile from the sprawling US Embassy.

Last week, the deputy head of Iran’s elite Revolutionary Guards said Iranian missiles can reach US warships in the Gulf, as tensions continued to rise between Washington and Tehran.

“Even our short-range missiles can easily reach (US) warships in the Persian Gulf,” Mohammad Saleh Jokar, the Revolutionary Guard’s deputy for parliamentary affairs, said, according to the semi-official Fars news agency.

“America cannot afford the costs of a new war, and the country is in a bad situation in terms of manpower and social conditions,” he added.

Iran has accused the United States of “psychological warfare” over the build-up of military forces, with foreign minister Javad Zarif saying there is “no possibility” of negotiations with the United States to reduce spiralling tensions.