Video has been released of Ukrainian helicopters flying supplies into the Azovstal plant in Mariupol even as it was under siege by Russian forces.
The video was shot aboard a Mi-8 helicopter and shows the aircraft flying low across countryside and then along the Mariupol shore before a brief shot of supplies being offloaded.
A social media channel affiliated with Ukrainian defense intelligence that distributed the video said the missions had been carried out by Ukrainian special forces.
Another channel that published the video said: "This unique special operation was carried out by specialists of the Main Intelligence Directorate of the Ministry of Defense and the Azov Regiment. 16 Mi-8 military helicopters loaded with the necessary equipment flew to the defenders of Mariupol blocked by Russia on Azovstal."
"There were 7 such missions in total. Each time, helicopters successfully delivered food, drinking water, medicines and ammunition to the defenders of the city to a depth of more than 100 kilometers [from Ukrainian-held areas]," the channel added.
Ukrainian President Volodymyr Zelensky referred to the previously undisclosed missions on May 20.
"Unfortunately, a large number of people died, our pilots. Absolutely heroic people who knew that it was difficult, that it was almost impossible to fly to Azovstal and bring there medicine, food, water, pick up the bodies of the wounded," he said.
"A lot of things were happening that no one could officially comment. There were no air corridors to Azovstal due to Russia's powerful deployed air defenses," Zelensky said.
The president added that "we lost a lot of pilots" who flew to the plant.