Demonstrators shouted slogans denouncing Iran's supreme leader in the restive southeast of the country on Friday, while a human rights group said at least 100 detained protesters were facing possible death sentences.

There have been demonstrations across the country against the clerical leadership since mid-September after the death in detention of a 22-year-old Kurdish Iranian woman arrested for wearing "inappropriate attire" under Iran's strict Islamic dress code for women.

"Death to the dictator, death to Khamenei!" protesters chanted in reference to Supreme Leader Ayatollah Ali Khamenei in a social media video said to be from Zahedan, capital of Sistan-Baluchistan province. Reuters could not verify the footage.

The impoverished province is home to Iran's Baluch minority of up to 2 million people, who human rights groups say have faced discrimination and repression for decades.

Some of the worst unrest in recent months has been in areas home to minority ethnic and religious groups with longstanding grievances against the state, such as in Sistan-Baluchistan and in Kurdish regions.

The protests, in which demonstrators from all walks of life have called for the fall of Iran's ruling theocracy, have posed one of the biggest challenges to the Shi'ite Muslim-ruled Islamic Republic since the 1979 revolution.

The government has blamed the unrest on demonstrators it says are bent on destruction of public property and are trained and armed by the country's enemies including the United States, Israel and Saudi Arabia.

State media gave wide coverage to large government-sponsored rallies that were held to condemn the unrest and pledge allegiance to clerical leaders.

CENTRAL BANK TO SUPPORT CURRENCY

Since the protests began more than three months ago, Iran's currency has lost a quarter of its value and fallen to a record low on the free-floating unofficial market as desperate Iranians have bought U.S. dollars and gold in an effort to protect their savings from inflation running at 50%.

On Friday, the country's new central bank governor, Mohammad Reza Farzin, told state TV that the bank would intervene in the foreign exchange market to support the rial.

"The (current) exchange rate is distorted ... and we will of course intervene in the free market," said Farzin, who was named on Thursday. 

Farzin said the central bank would set an exchange rate of 285,000 rials per dollar on Saturday on a state-run website where importers can buy hard currencies and that the bank would try to bring the free-floating dollar down to this level. The dollar is currently exchanged for about 420,000 rials.

Separately, a rights group said at least 100 detained protesters in Iran faced possible death sentences.

"At least 100 protesters are currently at risk of execution, death penalty charges or sentences. This is a minimum as most families are under pressure to stay quiet, the real number is believed to be much higher," the Norway-based Iran Human Rights group said on its website.

Iranian courts have so far handed down death sentences in more than a dozen cases based on Islamic law charges such as "warring against God" after convicting protesters of killing or injuring security forces, destroying public property and terrorising the public.

Amnesty international has condemned the "sham trials" and said many defendants were denied the right to access a lawyer of their own choosing and there was evidence of ill-treatment and forced "confessions" in some cases. Iranian authorities reject the accusations.