Sources say that the development comes after an agreement was reached between between Russian and Iranian high-level military-diplomatic officials. It gives Russian bombers the right to transit Iranian airspace and use at least two Iranian military airports for refueling.

Although unsaid, the development is most likely a response to recent US threats against the Syrian military – a close ally of both nations – following an alleged chemical attack in rural Damascus.

The information of development also comes after two Tu-95 and two Tu-22M heavy bombers were noted to have left their permanent base in Russia for an unknown destination.

During mid-2016, Russian Tu-22M bombers temporarily used the Iranian Hamadan Airbase amid a major bombing operation against Islamic State forces in eastern Syria.