Iran on Wednesday said it will not hand over the black box of the crashed Ukrainian airline jet to US planemaker Boeing. 

This comes amid tensions with the United States over the killing of General Qassem Soleimani and Iran's retaliation against US bases in Iraq. 

Boeing 737 jet of Ukraine International Airlines crashed shortly after taking off from Tehran's Imam Khomeini airport on Wednesday, killing all 176 people aboard.

The head of Tehran's civil aviation organisation said while the agency has decided not to send the black box to the US company, it is not clear which country it would be sent to so that its data could be analysed.

While the first statement by Ukraine's embassy in Iran referred to engine failure, its second statement said the causes had not been disclosed and that any previous comments were not official.

The plane was carrying 167 passengers and nine crew members from different countries including 82 Iranian nationals. There were also 11 Ukrainians and 63 Canadians on board the flight.