Ukraine's national security service says it is considering terrorism and an anti-aircraft missile as the two possible causes of the country’s airliner disaster in Iran that killed 176 people.

Service director Ivan Bakanov says the possibility of a terrorist attack is being carefully studied.

The US, meanwhile, promised “appropriate action” in response to its assessment an Iranian missile was responsible for downing the airliner.

Secretary of State Mike Pompeo has become the highest-level US official to directly pin the blame on Iran.

The Iranian government has denied playing a role.

It came as the Trump administration announced new sanctions on Iran following this week’s missile strikes by the Iranians in retaliation for the US killing of Revolutionary Guard General Qasem Soleimani.

The sanctions will target eight senior Iranian officials, as well as a range of industrial sectors. US officials have also revealed they tried, but failed, to take out Abdul Reza Shahla’i, a high-ranking commander in Iran’s Islamic Republican Guard Corps, on the day of the Soleimani strike.

President Donald Trump said on Friday that Iran was planning attacks on four American embassies when their top general was killed.