TEHRAN   -   Iran has freed nine of 12 Indian crew members of MT Riah, a Panama-flagged tanker it seized this month as part of a growing diplomatic crisis in the Middle East, the Indian foreign ministry said on Saturday.

The MT Riah was detained by the Iranian coastguard on 13 July, with 12 Indian crew members on board, the Indian foreign ministry said, and appealed for the release of the remaining crew. No reason has been provided as to why the three are being held.

“Nine crew members have been released and they will be on their way to India soon,” foreign ministry spokesman Raveesh Kumar said. “Our mission in Iran has requested the release of remaining crew members from the Iranian authorities concerned.”

Dozens of Indian sailors on ships in the Gulf have been caught up in rising tensions between Iran and the west.

Iranian state TV aired footage of the vessel a few days after it was seized, saying it had been detained by Iran’s elite Revolutionary Guards for smuggling fuel.

Indian and Iranian authorities said this week Iran had granted India consular access to 18 Indian crew seized on another ship, the British-flagged Stena Impero, that Iran seized in the Strait of Hormuz on 19 July.

The seizure of the British tanker in the world’s most important waterway for the oil trade has deepened a crisis between Iran and the west that was triggered in May when the US tightened sanctions, in effect barring all countries from buying Iranian oil.

Iran said it had seized the Stena Impero because it had collided with a fishing boat.

India’s junior foreign minister, V Muraleedharan, said India was pushing for the release of the Indian crew on the British vessel.

India has had longstanding political and energy ties with Iran, but it has cut all its oil supplies because of US sanctions. The release came on the same day that Oman’s top diplomat travelled to Tehran to discuss the escalation in the Gulf. Oman has maintained ties with Iran despite a freeze in relations between the Islamic republic and other GCC nations.

Oman’s minister responsible for foreign affairs held talks with Iran’s foreign minister on Saturday, Iranian state media reported.

Oman maintains friendly ties with both the United States and Iran and has previously been a go-between for the two countries, which severed diplomatic relations after the 1979 Iranian revolution. Iran’s Foreign Minister Mohammad Javad Zarif met Yousuf bin Alawi bin Abdullah, state television reported, without giving details of the talks.

“The visit was conducted in the framework of bilateral relations and continuous consultations of the two countries with the aim of exchanging views on recent regional developments, bilateral relations, ...and international issues,” state television reported.

Neither Oman nor Iran has confirmed that any mediation efforts are underway.

Tensions in the Gulf have soared since last year when President Donald Trump withdrew the United States from the 2015 nuclear deal with Iran and reimposed sanctions on the country.

In retaliation, Iran said in May it would disregard certain limits the deal set on its nuclear programme and threatened to take further measures if remaining parties to the deal, especially European nations, did not help it circumvent US sanctions.

Tensions have escalated further in the region with a string of incidents involving tankers and drones. The United States and Gulf powerhouse Saudi Arabia accused Iran of being behind multiple attacks on tankers in the Gulf in June, which Iran denies.

On July 19, a British-flagged tanker was impounded by Iran’s Revolutionary Guards with its 23 crew aboard in the Strait of Hormuz. The British ship is now in an Iranian port, along with its 23 crew members. The seizure was seen by London as a tit-for-tat move for British authorities detaining an Iranian tanker off the UK overseas territory of Gibraltar in early July. Oman has called for the release of the UK-flagged Stena Impero and for London and Tehran to resolve their dispute diplomatically.