The Iranian government declared on Sunday three days of national mourning for "martyrs" killed in recent protests, the state broadcaster reported.

The move came amid rising fatalities from two weeks of nationwide unrest, which Iran has blamed on the United States and Israel.

The semi-official Tasnim news agency reported that at least 111 members of Iran's security forces have been killed in clashes since the protests initially erupted over a sharp depreciation of the rial and sweeping subsidy reforms.

US-based rights group HRANA, meanwhile, said it had verified the deaths of 490 protesters and 48 security personnel, with more than 10,600 people arrested in two weeks of unrest.

However, these figures have not been independently verified and Iran has not given an official toll.

In response to the unrest, the government on Sunday called for nationwide rallies in support of the Islamic Republic on Monday.

In a televised interview with the state broadcaster IRIB on Sunday, Iranian President Masoud Pezeshkian stated that his government is prepared to address the economic grievances driving the protests, but warned that "rioters" will not be tolerated.

Pezeshkian also detailed the government's plans to implement a major subsidy reform program aimed at stabilising markets, boosting production, and increasing purchasing power, providing an update on its current progress.

The escalating violence has been accompanied by a sharp rise in regional tensions.

Iranian Parliament speaker Mohammad Bagher Qalibaf on Sunday threatened to retaliate against US and Israeli military assets across the Middle East if Washington launched strikes against Iran.

"If you take action to attack Iran, both the occupied territories and all American military centres, bases and ships in the region will be legitimate targets," Qalibaf told parliament.

His remarks followed reports that US President Donald Trump is considering military options to "protect" protesters.

Meanwhile, UN Secretary-General Antonio Guterres has urged Iranian authorities to exercise maximum restraint and enable access to information in the country, his spokesperson said on Sunday.

"The Secretary-General urges the Iranian authorities to exercise maximum restraint and to refrain from unnecessary or disproportionate use of force," spokesperson Stephane Dujarric said in a statement.

He further urges steps that enable access to information in the country, including restoring communications, the statement reads.

The flow of information from Iran has been hampered by an internet blackout since Thursday. (Xinhua/ Reuters)