An Iranian military transport aircraft carrying 302 people has crashed in the south of the country, killing all those on board.
The plane was on a flight between the town of Zahedan, near the border with Pakistan, and the central city of Kerman when it lost contact with air traffic control at about 1730 local time (1400 GMT).
The cause of the crash is not yet known, but air traffic controllers at Kerman airport said the pilot had radioed bad weather and strong winds before losing contact, the Iranian news agency IRNA reports. There has been heavy snow in the region.
IRAN AIR CRASHES
40 people die when a new Ukrainian plane crashes into a mountain in Iran in December 2002
Russian-made Tu-154 airliner crashes into mountains in March 2002, killing 117 people
80 die when a military plane crashes in north-east Iran in March 1997
Tu-154 crashes into a military plane near Tehran in February 1993, killing 132
Rescue workers have reached the scene of the crash and have begun sifting through the wreckage.
Iranian television said there were no survivors among the 284 elite Revolutionary Guards and 18 crew aboard the Russian-made Ilyushin plane.
The Guard, which was formed soon after the overthrow of the Shah and the creation of the Islamic republic more than 20 years ago, is seen as a staunch defender of Iran's Islamic regime.
IRNA said that some of the dead were believed to be senior security officials.
String of accidents
According to a local official in Zahedan, quoted by the Associated Press news agency, the Guards had been in the city to prepare for a visit by supreme leader Ayatollah Ali Khamenei.
The Iranian cabinet, in a statement,
has offered condolences to the nation and bereaved families over the "tragic event in which a group of IRGC [Revolutionary Guards] brothers" were killed.
There has been a series of disasters in Iran involving mainly Russian-built planes.
Up to half of Iran's transport aircraft are believed to be of Russian design, and correspondents say they have a poor safety record.
US sanctions have left Iran increasingly dependant on an ageing fleet, acquired from the former Soviet Union.
Three of them have crashed in the past two years, killing an estimated 200 people.
The most recent disaster was in December when a new Ukrainian plane flew into a mountain, killing more than 40 scientists on board, as it was preparing to land in Isfahan, about 400 kilometres (250 miles) south of the capital Tehran.