Iranian Foreign Minister Mohammad Javad Zarif told Reuters on Tuesday that Russia could use Iranian military bases to launch air strikes against militants in Syria on a “case by case basis.”

Russia and Iran are both key allies of Syrian President Bashar al-Assad and have played decisive roles in the past 18 months to turn the tide of the Syrian conflict in his favour.

Russian jets used an air base in Iran to launch attacks against militant targets in Syria last summer, the first time a foreign power had used an Iranian base since World War Two.

The deployment ended abruptly however after some Iranian lawmakers called the move a breach of Iran's constitution which forbids foreign military bases, and the Iranian defence minister chided Moscow for publicising the arrangement.

“Russia doesn't have a military base (in Iran), we have good cooperation, and on a case by case basis, when it is necessary for Russians fighting terrorism to use Iranian facilities, we will make a decision,” said Zarif.

Zarif is part of an Iranian delegation headed by President Hassan Rouhani, which arrived in Moscow on Monday.

The Iranian FM said that regional issues, including Syria, would be discussed at a meeting in the Kremlin with Russian President Vladimir Putin.