Trump has 'suspicions' over crash amid reports Iran downed plane

US President Donald Trump said Thursday he had "suspicions" about the crash of a Ukrainian airliner outside Tehran as US media reported it had been mistakenly shot down by Iran.

"I have my suspicions," Trump said.

"It was flying in a pretty rough neighbourhood and somebody could have made a mistake."

Trump's remarks came as Newsweek, CBS and CNN reported that the plane had been accidentally shot down by Iranian air defense systems.

All 176 people aboard died in the crash near Tehran on Wednesday.

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