US President Donald Trump on Thursday night reiterated his warning that the US would hit Iran “very hard" if its leadership kills protesters.

In an interview with Sean Hannity on Fox News, Trump said, “What they've done in the past, they've started shooting the hell out of people. And all of a sudden, people without any weapons whatsoever standing there and get machine guns, gunning them down, or they grab, take them to prisons and then hang them and kill them. So they played rough. And I said, if they do that, we're going to hit them very hard. We're going to hit them hard."

Trump added, “We're ready to do it. If they do that, we're going to hit them hard. And so far, for the most part, there's been some of it, but for the most part, they haven't. There have been people killed. Some of them, the crowds are so big that some of them have had, were stomped on. Literally. It was terrible."

“We'll see what happens. There's so many people protesting. Nobody's ever seen anything like what's happening right now. But I have put Iran on notice that if they start shooting at them..if they do anything bad to these people, we're going to hit them very hard."

Trump earlier on Thursday reaffirmed his backing for Iranian protesters as civilian unrest continues across the country.

“I have let them 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 an interview with radio host Hugh Hewitt.

When Hewitt noted that dozens have already been killed during the demonstrations, Trump responded that some deaths were the result of stampedes and not necessarily caused by law enforcement.

“I’m not sure I can necessarily hold somebody responsible for that, but … they’ve been told very strongly - even more strongly than I’m speaking to you right now - that if they do that, they’re going to have to pay hell," the President stated.

Reza Pahlavi, the Crown Prince of Iran, later condemned the Iranian regime for cutting off the Internet and other methods of communications as protests intensified, while thanking Trump for once again warning Iran against killing protesters.

“Millions of Iranians demanded their freedom tonight. In response, the regime in Iran has cut all lines of communication. It has shut down the Internet. It has cut landlines. It may even attempt to jam satellite signals," Pahlavi wrote in a post on social media.

“I want to thank the leader of the free world, President Trump, for reiterating his promise to hold the regime to account. It is time for others, including European leaders, to follow his lead, break their silence, and act more decisively in support of the people of Iran," he added.

“I call on them to use all technical, financial, and diplomatic resources available to restore communication to the Iranian people so that their voice and their will can be heard and seen. Do not let the voices of my courageous compatriots be silenced," concluded Pahlavi.

The comments came as Iranian protesters escalated their challenge to the country’s leadership, launching the largest demonstrations yet in nearly two weeks of rallies.

According to a report in Iran International, tens of thousands of people were taking part in demonstrations in major cities across Iran, including the capital, Tehran.

The Norway-based NGO Iran Human Rights (IHR) said that security forces had killed at least 45 protesters, including eight minors, since the demonstrations began.

In Tehran, footage posted to social media showed demonstrators chanting "death to the dictator" and "death to Khamenei".

On Wednesday night, protesters took to the streets in Ilam in western Iran and chanted “death to Khamenei."

Other footage posted to social media showed protesters destroying and toppling a statue of Qassem Soleimani, former head of the Quds Force of the Iranian Revolutionary Guards Corps (IRGC), in Fars Province.