A Russian delegation has arrived in Tehran for a visit that includes a meeting with Iranian President Masoud Pezeshkian, Russian state news agency TASS reports.
The group is being headed by deputy prime ministers Alexei Overchuk and Vitaly Savelev.
What relationship do Russia and Iran share?
Iran has been one of Russia's few staunch allies throughout the war against Ukraine and Western officials have also accused Iran of supplying Russia with weapons.
In September, US Secretary of State Antony Blinken said Iran had sent short-range ballistic missiles to Russia and the Kremlin "will likely use them within weeks in Ukraine".
And British Foreign Secretary David Lammy said the supply of ballistic missiles from Iran to Russia was "definitely a significant escalation" and said the UK was "coordinating".
Iran and Russia denied the claims.
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