The Iranian missile operator who shot down a Ukrainian passenger jet was acting alone when he opened fire because of a communications breakdown, a Revolutionary Guards commander said on Saturday. The operator had mistaken the Boeing 737 for a "cruise missile" and only had 10 seconds to decide whether to fire, said Brigadier General Amirali Hajizadeh, the Guards' aerospace commander.

"At various stages, it was reported... that cruise missiles had been fired towards the country," Hajizadeh said in remarks broadcast on state television.

The Ukraine International Airlines plane was brought down in Tehran hours after Iran launched a volley of missiles at US troops stationed at Iraqi bases on Wednesday.

All 176 people on board died.

"Given the information provided to the operator that it was a war situation and cruise missiles had been fired, this person identified this as a (missile)," Hajizadeh said.

"He was obliged to make contact and get verification. But apparently, his communications system had some disruptions.

"Either the 'jamming' system was the cause or the network was busy or whatever, he couldn't get in touch," said the Iranian general.

"He had 10 seconds to decide.

"Unfortunately under these circumstances, he made this bad decision, the missile was fired and the plane was hit and then... it turned and the spot that it crashed at was here," he said, pointing to a map.

The admission came after the Iran Civil Aviation Organisation rebuffed Western claims the plane had been shot down shortly after take-off from Tehran on Wednesday.