The carrier said the decision was taken after a "careful evaluation" using government security assessments and its own information.

Lufthansa first announced it had cancelled a flight from Frankfurt to Tehran last weekend to avoid the crew having to disembark and spend the night.

Middle Eastern countries and the United States have been on alert for a retaliatory attack by Iran since April 1, when the Iranian embassy compound in Syria was bombed by suspected Israeli warplanes.

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

(Writing by Friederike Heine; Editing by Miranda Murray, Andrey Sychev, Peter Graff)