German airline Lufthansa said it had suspended flights to Tehran due to the situation in the Middle East, which is on alert for possible Iranian retaliation for a suspected Israeli air strike on Iran’s embassy in Syria.

An Iranian news agency briefly stoked tensions when it published an Arabic report on social media platform X saying all airspace over Tehran had been closed for military drills. The agency then removed the report and denied it had issued such news.

Countries in the region and the United States have been on high alert and preparing for a possible attack by Iran since April 1 when Israeli warplanes were suspected of bombing the Iranian embassy compound in Syria.

Lufthansa said it suspended flights to and from Tehran from April 6 until probably April 11.

“We are constantly monitoring the situation in the Middle East and are in close contact with the authorities. The safety of our guests and crew members is Lufthansa’s top priority,” a spokesperson for the company told Reuters.

Lufthansa and its subsidiary Austrian Airlines are the only two Western carriers operating international flights into Tehran, which is mostly served by Turkish and Middle Eastern airlines.

Austrian Airlines, which is owned by Lufthansa and runs a direct Vienna-Tehran service six times a week, was still scheduled to operate its flight into Tehran on Thursday, according to its website and FlightRadar24.

There was no immediate word from other international airlines that fly to Tehran.

Iran’s supreme leader, Ayatollah Ali Khamenei, said that Israel “must be punished and it shall be” for the Damascus strike that killed seven Iranian Revolutionary Guards Corps members.

Among them was Mohammad Reza Zahedi, a senior commander in the Quds Force, an elite overseas unit of the Revolutionary Guards.

Israel, which launched a war in the Gaza Strip six months ago against Iran-backed Hamas, has not confirmed it was behind the strike on Damascus, but the Pentagon has said it was.

COULD STRIKES BE IMMINENT?

In an apparent response to Khamenei, Israeli Foreign Minister Israel Katz said Israel will respond if Iran attacks Israel from its own soil.

The United States and its allies believe major missile or drone strikes by Iran or its proxies against military and government targets in Israel are imminent, Bloomberg reported on Wednesday, citing U.S. and Israeli security sources.

U.S. Secretary of State Antony Blinken, in a call with Israeli Defense Minister Yoav Gallant, made clear that the United States would stand with Israel against any threats by Iran, the State Department said.

U.S. Middle East envoy Brett McGurk called the foreign ministers of Saudi Arabia, United Arab Emirates, Qatar and Iraq to ask them to deliver a message to Iran urging it to lower tensions, a source with knowledge of the situation said.

Iran’s foreign ministry said the foreign ministers of those countries spoke on the phone with Iran’s foreign minister and discussed regional tensions. The White House declined to comment.

Iran’s Revolutionary Guards shot down a Ukraine International Airlines passenger flight on Jan. 8, 2020 shortly after it took off from Tehran Airport at a time of heightened tensions between Tehran and Washington over the killing of a top Iranian commander in a U.S. drone strike at Baghdad airport.

Later, Tehran said that the downing of the Ukrainian airliner was a “disastrous mistake” by forces who were on high alert.

In retaliation for the killing of Qasem Soleimani, head of an elite overseas unit of the Guards, Iranian forces fired missiles at military bases housing U.S. troops in Iraq on Jan. 3.

Iran backs groups that have entered the fray across the region since Israel launched its invasion of Gaza.

More than 33,000 Palestinians have been killed in six months of Israeli bombardment of Gaza, according to the health ministry there. Hamas’ Oct. 7 attack on Israel killed 1,200 people, according to Israeli tallies.