US President Donald Trump has threatened the Iranian authorities with hitting them "very hard" if they kill the rioters.

“I have let them [i.e. the Iranian authorities] know that if they start killing people, which they tend to do during their riots… we’re going to hit them very hard,” Trump said, in particular, in an interview with radio host Hugh Hewitt.

There are reports of unrest in Iran, including in the capital Tehran. The internet is down in the country, and dozens of people, including police officers, have been killed and injured.