Ukrainian President Volodymyr Zelenskyy has called for the Iranian government to be held accountable, after Tehran admitted supplying drones to Russia.

Iranian Foreign Minister Hossein Amir-Abdollahian said on Saturday that Iran "gave a limited number of drones to Russia months before the Ukraine war."

It is the first time Iran has acknowledged sending drones Russia, but Zelenskyy called Tehran's timeline a "lie."

He said in a video message on Saturday that Iran claimed drones had been sent before the Russian invasion, but Ukrainian forces "shoot down at least ten Iranian drones every day."

He went on to say, "There will be no such thing in the modern world that any of the terrorists or their accomplices will remain unpunished."

Ukraine's Defence Minister Oleksii Reznikov told reporters on Friday that Iran plans to send Russia 1,500 to 2,400 drones, but Moscow has yet to receive all of them.

Iran had consistently denied allegations that it had supplied Russia with drones used for attacks in Ukraine.

Ukraine and Western countries have condemned Tehran for what they see as its support for Russia. The allegations prompted the United States and the EU member nations to impose sanctions on Iran.

Ukraine remains on high alert for Russia's continued use of Iranian-made drones, as fierce fighting continues in eastern Ukraine and other areas.

The Russian military is reportedly stepping up its offensive toward Bakhmut, one of the Ukrainian strongholds in the eastern Donetsk region.