US officials believe Iran accidentally shot down Ukraine airliner: Reports

US officials believe that Iran accidentally shot down a Ukrainian airliner, killing all of the 176 people on board, US media reported Thursday.

Newsweek, CBS and CNN quoted unnamed officials saying they are increasingly confident that Iranian air defence systems accidentally downed the aircraft, based on satellite, radar and electronic data.

"I have my suspicions," Trump. "It was flying in a pretty rough neighbourhood and somebody could have made a mistake."

"Some people say it was mechanical. I personally don't think that's even a question," Trump said, adding that "something very terrible happened."

The Ukraine International Airlines (UIA) Boeing went down outside Tehran shortly after take-off on Wednesday, killing all 176 people on board including many Iranians and Canadians.

The crash came shortly after Tehran launched missiles at bases in Iraq housing American troops to avenge the US killing of a top Iranian general last week.

Meanwhile, US President Donald Trump on Thursday also said he has his "suspicions over Iran".

Following the crash, investigators are pursuing several leads including a surface-to-air missile strike, an act of terror and engine failure, news agency AFP reported quoting Ukraine officials.

"For the moment we are working on seven different versions of the event that took place in Iran," Oleksiy Danilov, the secretary of Ukraine's national security and defence council (RNBO), told AFP.

The council is tasked with coordinating the probe into the disaster, the first fatal crash involving Ukraine's biggest carrier UIA.

The airline said the Boeing 737 had been built in 2016 and checked only two days before the accident. 

It said the pilots were well trained and that the plane's captain had more than 11,000 hours of flying experience, mostly on the Boeing 737.

Iranian authorities on Thursday said the plane turned around after taking off after suffering a "problem", disappearing from radars at an altitude of 2,400 metres (8,000 feet), but that the crew sent no message about an emergency.

(With inputs from AFP)