An air defense unit of the Iranian army "forgot" not to adjust the radar system, leading to a series of mistakes that caused the PS752 Ukraine plane to be shot down.

Iranian authorities have admitted that the air defense force made a mistake and shot down a civilian airliner of the International Airlines Ukraine bearing the number PS752 shortly after it took off on January 8, causing all 176 people.

According to a report published by the Iranian Civil Aviation Organization (CAO) on July 11, the Ukrainian plane was shot down by two missiles, firing 30 seconds from an air defense unit.

An officer in charge of control forgot to adjust the direction of the shooting on the radar system after moving to a new position.

"Air defense system officers launched missiles at what they perceived as hostile targets without a response from the command center," CAO said in the report, adding that the man acted maliciously.

Hours earlier, Iranian defenses were on high alert after Tehran launched a missile strike against US military bases in Iraq.

Iranian officials last month said six people were arrested after the incident but did not provide any further information.