The head of Iran's Revolutionary Guards ground forces and at least 10 other officers have died in a plane crash.
The government says an inquiry into the crash is under way
The small Falcon jet came down near Oroumieh, 900 km (560 miles) north-west of the capital, Tehran. State TV said it was attempting an emergency landing.
Officials blamed bad weather and engine failure for the crash.
Last month, a military transport plane crashed in Tehran, killing 128 people. It came down in a residential district, hitting a 10-storey apartment building.
The latest crash happened at around 0930 (0600GMT) near the Turkish border.
Revolutionary Guards' spokesman, Gen Masoud Jazayeri, said the plane "crashed near the airport due to bad weather, lack of visibility and failure in both engines."
On board was Ahmed Kazemi, the commander of the Revolutionary Guards ground forces and a veteran of the 1980-88 war with Iraq.
Correspondents say Gen Kazemi was one of the Guard's most powerful commanders after its commander-in-chief. He was recently appointed to the post by Iran's new president.
The Fars news agency, which has close links to the Revolutionary Guards, said a number of other top commanders, including an intelligence chief, were also on board.
Fars said 15 people were on the flight, and 13 had died with two missing. The Iranian news agency, Irna, said 11 people died in the crash.
The Revolutionary Guards, known locally as the Pasdaran, is a parallel military force with its own army, air force and navy.
It was set up to enforce and defend the principles of the 1979 Islamic revolution and answers directly to Supreme Leader Ayatollah Ali Khamenei.
Irna quoted deputy government spokesman Mohammad Paryab as saying an investigation into the causes of the crash would be carried out.
The military plane that crashed into the residential Tehran neighbourhood a month ago was carrying journalists to the south of the country.
The ageing plane - bought before the 1979 revolution - experienced technical problems and a first pilot refused to fly it, according to reports.
An inquiry into allegations of negligence has been carried out but not yet made public.
Because of US sanctions, Iran cannot buy spare parts of its ageing military and civilian fleet - something that puts lives in danger as air crashes become increasingly frequent, says the BBC's Frances Harrison in Tehran.