Germany has banned Iran's Mahan Air from landing in the country with immediate effect, citing security concerns and the airline's involvement in Syria, Al Jazeera reports.

Mahan Air is on a United States sanctions list and Washington has long urged allies to ban the airline from their territory.

The decision to ban the airline came after consultations with European allies and the US, Chancellor Angela Merkel's spokesman Steffen Seibert told reporters.

"It cannot be ruled out that this airline carries out transports to Germany that affect our security concerns," said Seibert.

"This is especially true against the backdrop of terrorist activities, intelligence on terrorist activities from the Iranian side and Iranian entities in Europe in the past."

US Secretary of State Mike Pompeo welcomed the German decision.

"The airline transports weapons and fighters across the Middle East, supporting the Iranian regime's destructive ambitions around the region," he said in a tweet. "We encourage all our allies to follow suit."

Mahan, Iran's second-largest carrier after Iran Air, flies four services a week between Tehran and the German cities of Duesseldorf and Munich.

The move comes at a time of sensitive relations with Iran. Germany plays a large role in trying to salvage the 2015 nuclear deal with Tehran after US President Donald Trump's decision to unilaterally pull out of it last year.