Major General Mohammad Bagheri, chief of staff of Iran’s military, says that statements condemning the supply were “mostly false” but showed “the effectiveness, importance and high rank" of Iran’s work on drones.
"The country's armed forces will continue to grow and develop their drones ... we will co-operate with other countries on drones," said Gen Bagheri, according to Iranian news agency Tasnim.
"Our drone systems are at a high ranking in the world in terms of accuracy, durability and continuity of operation and mission execution, and they perform various missions," he added.
Iran has admitted supplying what analysts call one-way attack drones — small unmanned aircraft fitted with explosives that fly directly into targets — claiming the weapons were supplied to Russia prior to the war.
Iran has also supplied a larger drone, which can be fitted with missiles, the Mohajer, which has also been supplied to allied militias in Iraq.
Ukraine says it has shot down scores of drones since August, when the US said Iran had sent hundreds of the aircraft to Russia. The most popular aircraft sent is believed to be the Shahed-136 model, which has been used widely by Iran and its allies, including Houthi militias in Yemen, to attack energy infrastructure and shipping in the Middle East.
The drones have been used in a similar way in Ukraine, attacking large energy infrastructure targets such as power stations, knocking at least 10 gigawatts of power out of Ukraine’s 50-gigawatt capacity. Millions have been left without power or heating as night temperatures plummet far below zero.
Russia is said to be running low on accurate missiles and drones — dubbed precision-guided munitions by analysts. Both sides are said to be low on artillery ammunition, leading to fears that the conflict will enter a prolonged stalemate.
The high intensity of the conflict in Ukraine, which often results in Russia launching scores of missiles and explosive drones in a single wave of attacks, has depleted Russia’s arsenal.
Western sanctions targeting component suppliers, including companies supplying microchips for sensors and navigation equipment for drones and missiles, has slowed Russia’s capacity to manufacture enough of the weapons.
The supply of Iranian drones to Russia has sparked fury in Europe and the US, with some diplomats going as far as saying it has stopped any possibility of renewing a 2015 nuclear deal to ease sanctions in exchange for Iran accepting UN inspections of nuclear sites.
In September, the EU foreign policy chief Josep Borrel said: “We simply don't see a deal coming together anytime soon, while Iran continues to kill its own citizens and is selling UAVs [unmanned aerial vehicles] to Russia.”
The US and EU have hit Iran with new sanctions over the drone supply, which threatens to undermine a $60 billion western effort to equip Ukraine with weapons to fend off Russia's invasion.
Germany has supplied air defence weaponry to counter the drones, including the Gepard anti-aircraft gun system and the IRIS-T missile system. Last month, the US also sent a Norwegian missile system, which fires rockets normally designed for air-to-air combat.
Earlier this week, the US said it would supply Ukraine with the Patriot air defence missile system, one of the most advanced of its kind in the world, which is primarily designed to intercept missiles but can also be used against drones.