The United Nations on Tuesday denounced Iran's increasingly harsh and deadly crackdown on mass protests that have been rocking the country for more than two months, AFP reported.

"UN Human Rights Chief Volker Turk says the rising number of deaths from protests in Iran, including those of two children at the weekend, and the hardening of the response by security forces, underline the critical situation in the country," spokesman Jeremy Laurence told reporters in Geneva.

"We urge the authorities to address people's demands for equality, dignity and rights, instead of using unnecessary or disproportionate force to suppress the protests," he said.

"The lack of accountability for gross human rights violations in Iran remains persistent and is contributing to the growing grievances."

His comments came after Iranian security forces on Monday intensified their crackdown in western Iran's Kurdish-populated regions, directly shooting at protesters, using heavy weapons and killing a dozen people over 24 hours, rights groups said.

The Kurdish-populated provinces of western and northwestern Iran have been hubs of protest since the death in custody of 22-year-old Kurdish woman Mahsa Amini on September 16, after she was arrested by morality police in Tehran.