A nationwide internet blackout was reported in Iran on Thursday, internet monitoring group NetBlocks said, as protests over economic hardships continued around the country.

No further information on the internet outage was immediately available.

Xinhua News Agency said its Tehran-based reporters experienced the blackout, starting from around 8.15 pm local time.

The blackout comes amid ongoing protests in several Iranian cities since late last month, including the latest in Tehran on Thursday, over the sharp fall in the rial and long-standing economic hardships.

Iran's semi-official Mehr news agency reported on Thursday that 23 police officers and one "rioter" were injured during clashes in northeastern Iran's Khorasan Razavi over the past days, amid protests in the province.

Five people were killed in an attack by "rioters" on a police station in the province on Wednesday night, it added.

As the unrest continues, US President Donald Trump on Thursday threatened again to strike Iran "very hard" if its authorities "start killing people".

"I have let them know that if they start killing people ... we are going to hit them very hard," Trump said in an interview with a conservative radio host.

Trump and other senior US officials recently warned on several occasions that Washington would act if Iran "kills peaceful protesters."

On Wednesday, Iran's Foreign Ministry condemned what it described as "interventionist and deceptive" remarks by the Trump administration on recent unrest in the country, saying they reflected Washington's continued hostility toward the Iranian people.

The US comments on Iran's internal affairs were part of a long-standing policy of pressure and interference, rather than genuine concern for the welfare of Iranians, said the ministry in a statement. (Xinhua/ Reuters)