Iran on Saturday seized an Israel-linked vessel reportedly carrying 17 Indian sailors, as tensions in West Asia came to a head on Saturday, with at least six international airlines, including Air India and Vistara, altering operations in the region amid a widely expected Iranian retaliation to Tel Aviv’s bombing of its embassy in Syria on April 1. India is in touch with Tehran to secure the early release of the sailors, people familiar with the matter said.

The escalation came hours after people familiar with western intelligence assessments, according to Bloomberg, said that Israel is bracing for a direct and unprecedented attack by Iran on government targets as soon as the weekend, a move that has the potential to trigger an all-out regional war.

“I don’t want to get into secure informatio,n but my expectation is sooner rather than later,” US President Joe Biden said on Friday in response to a question about whether an Iranian strike was imminent. Asked what message he’d give to Iran, Biden responded, “Don’t.”

According to media reports, a special forces unit of Iran’s Islamic Revolutionary Guard Corps on Saturday seized MSC Aries, whose beneficial owner is Zodiac Maritime Ltd, part of Israeli businessman Eyal Ofer’s Zodiac Group, near the Strait of Hormuz between the Persian Gulf and Gulf of Oman. Iranian forces are directing the ship to Iranian waters, Iran’s official news agency IRNA said, without giving a reason for the seizure. The vessel, sailing under the Portuguese flag, had most recently stopped at Khalifa Port in the United Arab Emirates, according to ship-tracking data compiled by Bloomberg.

India is in touch with Iranian authorities through diplomatic channels, both in Tehran and New Delhi, to ensure the security and early release of 17 Indian nationals who are among the 25-member crew of the ship, people familiar with the matter told HT. The 17 Indians on board the vessel include the master. The crew also includes four Filipinos, two Pakistanis, one Russian and one Estonian.

“We are aware that the cargo ship MSC Aries has been taken control of by Iran. We have learnt that there are 17 Indian nationals on board,” one of the people cited above told HT on condition of anonymity.

MSC confirmed the Aries had “been boarded by Iranian authorities via helicopter as she passed the Strait of Hormuz” on Saturday morning. It said that it was “working closely with the relevant authorities to ensure the well-being of the crew, and safe return of the vessel”.

A video shared on social media appeared to show people descending from a helicopter onto the deck of the Aries using a rope.

After the seizure, Israel warned that Iran would suffer the “consequences for choosing to escalate the situation any further”. Tehran has vowed to avenge a suspected Israeli strike on April 1 on an Iranian consular building in the Syrian capital of Damascus that killed 12 people, including a senior Guard general who once commanded its expeditionary Quds Force there.

Following Iran’s retaliation threats, Israel said it was strengthening air defences and paused leave for combat units. A US defence official in Washington said that “we are moving additional assets to the region to bolster regional deterrence efforts and increase force protection for US forces”.

The surging tensions come against the backdrop of Israel’s war against Palestinian militant group Hamas in Gaza, now in its seventh month. Gaza truce talks which started on Sunday in Cairo have brought no breakthrough on a plan presented by US, Qatari and Egyptian mediators, which Hamas has said it was studying.

One of the people familiar with the matter told Bloomberg it’s possible that the increasingly inflammatory rhetoric between Israel, Iran, and the US could be grandstanding, but said the working assumption for Israel and allies is that an attack is imminent. Diplomatic back-channels are in overdrive, Bloomberg reported.

Meanwhile, Air India and Vistara were among the airlines that adjusted their flights paths to avoid risky airspace in the region. It was not exactly clear what the new route modifications would be, but people aware of the development in both airlines said the tweaks would only add some extra minutes to journey durations for most sectors, without giving details.

“We are closely monitoring the developing situation in the Middle East. Presently, our aircraft will operate on alternate flight paths to and from India — according to top priority to the safety of our passengers and crew,” an Air India spokesperson said.

“Due to the current situation affecting parts of the Middle East, we are making changes to flight-paths of some of our flights. Contingency routes, which are kept available to ensure operational continuity during such eventualities, are being used instead. This may result in longer flight times on certain routes and associated delays. The situation is being monitored closely and further changes will be made if required,” a Vistara spokesperson said.

German airline Lufthansa said its planes would no longer use Iranian airspace, while its subsidiary Austrian Airlines made a similar move. Australian airline Qantas said its long-haul Perth-London flights would also avoid Iranian airspace. Dutch airline KLM will no longer fly over Israel and Iran.

France earlier warned its nationals against travelling to the region, while the US embassy in Israel said it was restricting the movements of its diplomats over security fears. Canada warned citizens to avoid all travel to Israel, Gaza and the West Bank, upgrading its risk assessment of the region due to the increased threat of attacks on Israeli territory.

The Netherlands said that its embassy in Tehran and consulate in Arbil, Iraq, would remain closed on Sunday “in connection with the rising tensions between Iran and Israel”.

Saturday’s seizure also widened concerns around commercial shipping in the West Asia since the outbreak of fighting between Israel and Hamas, the Palestinian militant group in Gaza that’s backed by Tehran, on October 7.

Risks have so far been focused in the Red Sea, where Iran’s Yemeni allies the Houthis have repeatedly targeted ships in the Red Sea that they say are linked to Israel or its allies. But the seizure brought attention back to the Strait of Hormuz, which connects the Gulf with the Indian Ocean and is a key choke point for energy shipments through which around a fifth of the world’s daily oil supply passes.

Oil jumped to the highest level since October on the news, rallying as much as 2.6% to top $92 a barrel.

The head of IRGC’s naval forces, Alireza Tangsiri, said on Tuesday that Iran has the option of blocking the Strait of Hormuz amid rising tensions with Israel but has chosen not to.

“An already bad situation in the Red Sea and Gulf of Aden has just got worse and could put ocean freight container imports and oil exports in the Middle East at risk,” said Peter Sand, chief analyst at Oslo-based shipping-analytics company Xeneta. “If ships are impacted from sailing into the Arabian Gulf then the disruption would be considerable.”