Iran's president has said the downing of a plane in Tehran is an "unforgivable error" – and all those involved will be punished.
In a televised speech on Tuesday, Hassan Rouhani added that the "tragic event" would be investigated thoroughly, claiming "one person cannot be solely responsible for the crash".
He added: "Iranian armed forces admitting their mistake is a good first step.
"We should assure people that it will not happen again" – but said his government was "accountable to Iranian and other nations who lost lives".
Iran's judiciary spokesman, Gholamhossein Esmaili, has said some people have been arrested for their role in the incident – but he did not give any further details.
Ukrainian Prime Minister, Oleksiy Honcharuk, said there were 167 passengers and nine crew members on the Ukraine International Airlines flight to Kiev.
Initially, Iranian state television said flight PS 752 came down due to what it described as "technical problems" after leaving Imam Khomeini airport.