Air India flights have begun avoiding Iranian airspace amid soaring Middle East tensions as warnings grew of retaliation for Israeli strike on Iran's embassy in Damascus earlier this month, sources said today.

A London-bound Air India flight took longer route to avoid Iranian airspace this morning, tracking website Flightradar24 showed.

All Air India flights bound for Europe could now take upto 45 minutes longer to reach the destination, sources said.

Air India flights to the Middle East, however, will not be impacted as they fly South of Iranian airspace.

The 'shadow war' between the two Middle Eastern countries heated up when an Israeli airstrike hit the Iran consulate in Damascus on April 1, killing seven people, including two generals.

US and other intelligence assessments have said the retaliation could come as soon as Sunday. The unprecedented attack could trigger an all-out regional war.

Iran's supreme leader, Ayatollah Ali Khamenei, had earlier this week warned that Israel "must be punished and will be punished", days after one of his advisers said Israeli embassies are "no longer safe".

The Israeli military said it had not issued fresh instructions to civilians, but that its forces were on high alert and prepared for a range of scenarios.

Countries including India, France and Russia have warned their citizens against travel to the region, already on edge over the war in Gaza, now in its seventh month.

Since Iran viewed the embassy strike as equivalent to an attack on its own territory, sources say, a direct attack on Israeli soil by Iran itself rather than a proxy such as Hezbollah in Lebanon was a real possibility.

US President Joe Biden also said that he was expecting Iran to attempt to strike Israel in the short term and pledged "ironclad" support for Washington's top regional ally despite diplomatic tensions over Israel's military conduct in Gaza. "We are devoted to the defense of Israel, we will support Israel, we will help defend Israel and Iran will not succeed," he said.