Donald Trump has praised protesters for challenging Iran's 'brutal and corrupt' regime after a Tehran official warned demonstrators face the death penalty.

After days of unrest that have seen 21 people killed and more than 450 arrested, the US President said Iranians were 'finally acting'.

'All of the money that President Obama so foolishly gave them went into terrorism and into their 'pockets.' The people have little food, big inflation and no human rights. The U.S. is watching!' he wrote this morning.

Iran's foreign ministry hit back saying Trump should focus on 'homeless and hungry people' in his own country rather than insulting Iranians.

'Instead of wasting his time sending useless and insulting tweets regarding other countries, he would be better off seeing to the domestic issues of his own country such as daily killings of dozens of people... and the existence of millions of homeless and hungry people,' said ministry spokesman Bahram Ghasemi.

It comes after nine people died in overnight clashes and the head of Tehran's Revolutionary Court reportedly warned detained protesters could be executed.

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The death toll from violent protests in Iran has risen to 21 after nine more people were killed in clashes overnight. New pictures have emerged showing some of the unrest on New Year's Eve with a building on fire in Dorud

Six of the most recent decent deaths happened when protesters clashed with security forces as they tried to storm a police station in Qahderijan, a town of 30,000 in the Isfahan region of central Iran. People stand near a burning car in Tuyserkan, Hamadan Province, Iran on December 31

Supreme Leader Ayatollah Ali Khamenei (pictured today) has blamed the country's 'enemies' for riots that have claimed nine more lives overnight

Iranian President Hassan Rouhani (pictured) has dismissed the protests taking place across Iran on Monday as 'nothing', in a bid to downplay the significance of the increasingly violent demonstrations

Donald Trump has praised protesters for challenging Iran's 'brutal and corrupt' regime after a Tehran official warned demonstrators face the death penalty. In a tweet, the US President said saluted Iranians for 'finally acting' after days of unrest that have seen 21 people killed and more than 450 arrested

Mousa Ghazanfarabadi said: 'Obviously one of their charges can be Moharebeh,' or waging war against God. That's a death penalty offense in Iran. He was also quoted as saying some protesters will come to trial soon on charges of acting against national security and damaging public properties.

It comes after Iran's supreme leader Ayatollah Ali Khamenei blamed the country's 'enemies' for the riots. Khamenei is said to have met with top political leaders and security chiefs to discuss a clamp down on protests.

A report of the meeting states: 'God help us, this is a very complex situation and is different from previous occasions.'

The documents emerged as nine were killed in clashes overnight bringing to 21 the total number of those killed in the unrest so far. Six deaths happened when protesters clashed with security forces as they tried to storm a police station in Qahderijan, a town of 30,000 in the Isfahan region of central Iran.

A member of the Revolutionary Guards and a passer-by were killed in nearby Kahriz Sang. Around 100 people were arrested overnight in the same region, Iranian state television reported.

Khamenei this morning said enemies of the Islamic Republic had stirred unrest, using 'different tools including cash, weapons, politics and intelligence apparatus to create troubles'.

According to Fox News, a leaked report of his meeting was given to the National Council of Resistance of Iran by senior government sources. It suggested the protests have hit the country's economy and 'threatens the regime's security'.

'The first step, therefore, is to find a way out of this situation,' it added.

Twelve people have been reported dead during a fourth straight night of protests in Iran, including reports of three people killed in the city of Isfahan

Video purportedly taken in Isfahan on Sunday night shows dozens of people on the street before what sounds like gunshots are heard

Khamenei this morning said enemies of the Islamic Republic had stirred unrest, using 'different tools including cash, weapons, politics and intelligence apparatus to create troubles'

'Religious leaders and the leadership must come to the scene as soon as possible and prevent the situation (from) deteriorating further. God help us, this is a very complex situation and is different from previous occasions.'

Despite the unrest, Iranian President Hassan Rouhani yesterday dismissed the protests as 'nothing'

Earlier reports had already said a policeman was killed and three others injured in Najafabad after being shot with a hunting rifle.

That brings the estimated death toll to 21 in unrest linked to the protests, that began last Thursday in second city Mashhad and quickly spread across the country.

The unrest has remained focused on provincial towns and cities, with only sporadic protests reported in Tehran on Monday evening.

Some 450 people have been arrested in the Iranian capital, an official told local media on Tuesday.

'200 people were arrested on Saturday, 150 on Sunday and around 100 on Monday,' Ali-Asghar Naserbakht, a deputy in the Tehran city governor's office, told the reformist-linked ILNA news agency.

IRAN BLOCKS SOCIAL MEDIA IN BID TO STOP SPREAD OF UNREST Iran has shut down social media in an attempt to stop unrest from spreading widely as deadly anti-government protests continue across the country. Authorities have blocked access to Instagram and the Telegram messaging app as part of a clamp down on its citizens' internet communications. Meanwhile, Google has faced calls to lift restrictions on its services for internet users in Iran so that millions of protesters can 'connect and organise'. President Hassan Rouhani has insisted people are 'absolutely free' to express their anger but 'criticism is different to violence and destroying public property.' But the demonstrations, which have claimed 21 lives and led to 450 arrests so far, were fanned in part by messages sent on social media platforms prompting a black out of some services on Sunday. Iran has shut down social media in an attempt to stop unrest from spreading widely as deadly anti-government protests continue across the country. An iranian man is pictured showing how one of his apps is no longer functioning Telegram in particular is very popular in Iran, with more than 50 per cent of the country's 80m population said to be active on the app. Iran state TV website reported the decision citing an anonymous source who said it was 'in line with maintaining peace and security of the citizens.' The source said: 'With a decision by the Supreme National Security Council, activities of Telegram and Instagram are temporarily limited.' Google meanwhile has been urged to lift internet restrictions in the country. Dr Steven Murdoch, a security researcher in the Computer Science Department, University College London, told Sky News that Google blocks users from Iran from accessing many of its services because of US sanctions. But as a result, people have encountered difficulties trying to use counter-censorship apps such as Signal, which was set up to bypass blocking by disguising itself amongst Google's services. NSA whistleblower Edward Snowden later tweeted: 'Many US politicians say they want to help Iranian protesters. If they're serious, one phone call could get @Google to restore millions of protesters' ability to connect and organize.' Google has not yet responded to requests for comments, Sky said. Advertisement

Iran's reformist politicians on Tuesday condemned violence that has rocked the country in recent days, accusing the US of stirring unrest while still calling on their government to address economic grievances.

'Without doubt the Iranian people are confronted with difficulties in their daily lives... and have the right to peacefully demand and protest,' said a statement from the Association of Combattant Clerics, headed by reformist ex-president Mohammad Khatami.

'But the events of recent days have shown that opportunists and trouble-makers have exploited the demonstrations to create problems, insecurity and destroy public buildings, while insulting sacred religious and national values.'

Khatami led the country from 1997 to 2005 but was later barred from public appearances for his role in leading mass demonstrations in 2009.

The group said the violence seen through five days of protests across the country would help Iran's 'enemies'.

'The enemies of Iran, headed by the United States and their agents... have encouraged the trouble-makers and the violent actions.'

Protests have been relatively small in Tehran compared with many parts of the country since the unrest began last Thursday.

'We feel the situation in Tehran is more calm than previous days. Already yesterday, it was calmer than before,' said Naserbakht.

He added that no request had yet been put to the Revolutionary Guards to intervene in the capital.

Crowds continued to gather in Iran despite the government blacking out the Telegram messaging app and Instagram

Police have used water cannon to disperse protesters who had gathered in Ferdowsi Square, Tehran

'We will not permit insecurity to continue in any way in Tehran. If it continues, officials will take decisions to finish it,' said Esmail Kowsari, a deputy commander for a local branch of the Revolutionary Guards, on state television.

Rouhani yesterday attempted to downplay the significance of the mass demonstrations.

In what has become the biggest threat to Iranian leaders since the presidential protests in 2009, Rouhani's words have so far failed to quell the increasingly violent uprising.

'Our great nation has witnessed a number of similar incidents in the past and has comfortably dealt with them. This is nothing,' Rouhani said in a meeting with Iranian members of parliament on Monday, CNN reported.

Ali Shamkhani, secretary of Iran's Supreme National Security Council, described the unrest - the biggest challenge to the regime since mass protests in 2009 - as a 'proxy war against the Iranian people'.

'Hashtags and messages about the situation in Iran come from the United States, Britain and Saudi Arabia,' he told local media.

Iran's intelligence ministry released a statement saying 'instigators' have been identified 'and will be dealt with seriously soon'.

Hassan Rouhani said people were 'completely free to express their criticism' of the government but violence would not be tolerated in his first public remarks on the crisis

Protests started in the north east city of Mashhad last week but have since spread around the country in the most serious challenge to the regime since 2009

The Revolutionary Guards have yet to fully intervene against the protesters, but published photos on Monday of three wanted people and called on the public to report any 'seditionist elements'.

Pro-regime rallies were held across several towns and cities - reflecting continued support among a large conservative section of society.

Reporting restrictions remained tight, but videos on social media continued to show widespread anti-government protests in many areas.

Rouhani came to power in 2013 promising to mend the economy and ease social tensions, but high living costs and a 12 percent unemployment rate have left many feeling that progress is too slow.

The young are most affected, with as many as 40 percent out of work according to analysts, and rural areas particularly hard-hit.

'People have had enough, especially the young people. They have nothing to be happy about,' said Sarita Mohammadi, a 35-year-old teacher in Tehran.

'The situation is far worse in provinces. Agriculture has been destroyed. I know many who have left the north of the country to come to Tehran to work,' she added.

Rouhani acknowledged there was 'no problem bigger than unemployment' in a speech on Sunday, and also vowed a more balanced media and more transparency.

President Trump continued his attacks on the Iranian regime via Twitter as Rouhani said he has 'no right to feel pity for the people of Iran'

US President Donald Trump, who has repeatedly criticised Tehran over four days of demonstrations, said it was 'time for a change' and that Iran's people were 'hungry' for freedom.

The European Union on Monday pushed Iran to guarantee the right to protest and separately British Foreign Secretary Boris Johnson said 'the UK is watching events in Iran closely'.

'We believe that there should be meaningful debate about the legitimate and important issues the protesters are raising and we look to the Iranian authorities to permit this,' Johnson said in a statement.

In 2009, authorities ruthlessly put down protests against the re-election of hardliner Mahmoud Ahmadinejad. At least 36 people were killed in 2009, according to an official toll, while the opposition says 72 died.