A Ukrainian aircraft which crashed earlier this week in Iran had flown close to a sensitive military site belonging to the elite Revolutionary Guards and was shot down unintentionally due to human error, the Iranian military said in a statement read on state TV on Saturday.
The responsible parties would be referred to a judicial department within the military and held accountable, the statement said.
President Hassan Rouhani also confirmed the development and said that Iran "deeply regrets the disastrous mistake".
In a series of tweets posted on Saturday, Rouhani promised that investigation would continue to "identify and prosecute this great tragedy and unforgivable mistake".
"The Islamic Republic of Iran deeply regrets this disastrous mistake," he wrote on Twitter. "My thoughts and prayers go to all the mourning families. I offer my sincerest condolences."
All 176 people on board were killed in the crash. The Iranian military statement expressed condolences to the families of the victims.
The United States and Canada had said that the plane was shot down, a claim Iran had initially denied.
Meanwhile, Iran Foreign Minister Javad Zarif in a tweet confirmed the finding and expressed his sorrow over the loss of lives. "A sad day. Preliminary conclusions of internal investigation by Armed Forces: Human error at time of crisis caused by the United States adventurism led to disaster."
"Our profound regrets, apologies and condolences to our people, to the families of all victims, and to other affected nations," he added.
Ukraine, Canada demand accountability, compensation
Hours after Tehran admitted on Saturday that she had unintentionally downed the Ukrainian jetliner, Ukraine President Volodymyr Zelensky demanded that Iran punish those responsible for the downing and pay compensation.
“We expect Iran... to bring the guilty to the courts,” the Ukrainian leader wrote on Facebook, calling also for the “payment of compensation” after Tehran admitted accidentally downing the plane and killing all 176 people on board.
Similarly, Canada's Prime Minister Justin Trudeau said closure and accountability were needed after Iran said it had unintentionally shot down a Ukrainian plane.
He also demanded “transparency, and justice for the families and loved ones of the victims,” of whom many were Canadian dual nationals.
“This is a national tragedy, and all Canadians are mourning together,” Trudeau's office said in a statement.
Russia also reacted to the admission as the chairman of the Russian parliament's foreign affairs committee said that Iran must “learn lessons” from the disaster.
“If decryption of the black boxes and the work of the investigation do not prove that the Iranian army did this intentionally, and there are no logical reasons for this, the incident must be closed.
“Hoping that lessons will be learned and action taken by all parties,” said Konstantin Kosachev, quoted by the Interfax news agency.