An Iranian domestic airliner has crashed into the country's Zagros mountains, and officials fear all 65 people on board were killed.
The flight left Tehran Sunday morning for the city of Yasuj in the Isfahan province, a flight of some 560 kilometers.
The Iranian Red Crescent said it has deployed teams to the area, but dense fog, high winds and heavy snow made it impossible for the helicopters to get close to the crash site.
The United Nations said Secretary-General Antonio Guterres joined world leaders in expressing sorrow over the crash. The U.N. said Guterres "was deeply saddened to learn of the tragic airplane accident" and extended his "heartfelt condolences" to the families of the victims and the people of Iran.
Decades of international sanctions have left Iran with an aging commercial airline fleet, and accidents have increased in recent years. The country has been unable to buy airplane parts for needed maintenance or upgrade its fleet.
Following the 2015 nuclear deal with world powers, Iran signed agreements with both Airbus and Boeing to buy new planes.