Mahdi said in a statement on November 29 he would submit his letter of resignation to parliament so lawmakers could select a new government.

Mahdi, 77, took office just over a year ago. The statement did not say when his resignation would occur.

Earlier in the day, Iraq's top Shi'ite cleric, Grand Ayatollah Ali al-Sistani, condemned the use of force against protesters and called for lawmakers to drop their support for the current cabinet and also urged demonstrators to reject acts of violence and vandalism.

The call came a day after more than 40 people were reported killed in one of the bloodiest days of protests.

Iraqis have been taking to the streets of Baghdad and the country’s Shi'ite-majority south since early October to demand more jobs, an end to endemic corruption, and improved public services.

In remarks delivered by his representative during a televised Friday Prayers sermon in the city of Karbala, Sistani said the government appeared to have been "unable to deal with the events of the past two months."

"Parliament, from which the current government emerged, must reconsider its choices and do what's in the interest of Iraq," the cleric said.

UN Secretary-General Antonio Guterres said he was "deeply concerned over reports of the continued use of live ammunition against demonstrators."

On November 29, casualties were reported in clashes between protesters and security forces in Nasiriyah, where most of the deaths the day before occurred.

There were also reports that protesters were killed in Baghdad.

On November 28 in Nasiriyah, at least 25 people were killed when security forces used live ammunition and tear gas to clear two bridges occupied by protesters, while demonstrators torched a police station, according to medics and security sources.

Reports said live rounds were also fired at Baghdad's Ahrar Bridge as protesters tried to cross toward the Green Zone that hosts parliament and government buildings. Four people were reported killed.

Four more people were reported killed in clashes the southern city of Najaf.

The Iraqi military said on November 28 that "crisis cells" were set up in several provinces to try to "impose security and restore order."

The U.S. State Department said it shared the protesters' "legitimate concerns" and urged the Iraqi government to "advance the reforms demanded by the people, including those that address unemployment, corruption, and electoral reform."

It did not comment directly on Mahdi's decision to quit.

With reporting by Reuters, dpa, AFP, and the BBC