""We are still hopeful but information coming from the crash site is very concerning," they added.Iran is one of Russia's closest allies on the international stage. The two countries have only deepened their military and political cooperation since the start of the full-scale invasion of Ukraine in February 2022.Most notably, Iran has provided Russia with thousands of Shahed kamikaze drones used in airstrikes against Ukraine and has helped Moscow build a drone factory in Russia, as well as reportedly sending thousands of ballistic missiles.Iranian state media said the helicopter made a "hard landing" near the city of Tabriz in the north-west of the country.Rasi and his entourage were returning in a convoy of three helicopters from a trip to the border with Azerbaijan where he opened two new dams.A rescue operation is underway but is being hampered by both the terrain and weather.Explainer: Iran’s cheap, effective Shahed drones and how Russia uses them in UkraineEditor’s note: This story initially said that Shahed-136 drones are said to weigh 10-15 kilograms.