Deutsche Lufthansa AG has suspended services to Tehran amid an escalation in tensions in the Middle East.

The German flag carrier said that the halt began on April 6 and will continue until April 13, according to a spokeswoman. The airline’s Frankfurt-Tehran service requires an overnight layover for crews. 

Austrian Airlines, owned by Lufthansa, flies to Iran from Vienna in same-day return service and is scheduled to operate this evening, according to FlightRadar24.

Tensions in the Middle East are soaring after the US warned that possible missile or drone strikes by Iran or its proxies against Israel were imminent, in retaliation for an attack on a diplomatic compound in the Syrian capital of Damascus last week that killed senior Iranian military officials.

Lufthansa and Austrian Airlines are the only two Western carriers still operating services to Tehran, although the Iranian capital is served by carriers including Qatar Airways, Flydubai, Emirates, Oman Air, Turkish Airlines, Pegasus, Corendon Airlines, and Air Arabia.

The German carrier was the first foreign airline to resume flights to Israel in January after suspending the service in the wake of   of the conflict between Hamas and Israel.