Those responsible would be held accountable, the statement said.
Iran had previously rejected suggestions that one of its missiles brought down the plane near the capital, Tehran, on Wednesday.
But pressure mounted after the US and Canada, citing intelligence, said they believed Iran had shot down the plane with a missile, possibly accidently.
The downing of Ukraine International Airlines flight PS752 with the loss of 176 lives came just hours after Iran carried out missile strikes on two airbases housing US forces in Iraq.
The Ukrainian flight, which was headed to the Canadian city of Toronto via the Ukrainian capital, Kyiv, came down near Imam Khomeini Airport shortly after take off.