Updated

Security forces have launched a search operation to determine the source of three mortar shells that landed inside Baghdad's heavily fortified Green Zone, following a night of violent confrontations between protesters and security forces in the country's south in which three people were shot dead.

There was no immediate claim of responsibility for the mortar shells that landed just after midnight Friday in an abandoned lot in the Green Zone, and no casualties were reported.

The rare attack comes amid a political crisis and worsening protests against poor services and unemployment in the southern city of Basra, which have turned violent in the past few days.

Hundreds of angry protesters in Basra took to the streets on Thursday night. Some clashed with security forces, lobbing Molotov cocktails and setting fire to a government building as well as the offices of Shiite militias. At least three people were shot dead in confrontations with security forces.

Residents of Basra and other cities in Iraq's oil-rich southern Shiite heartland have been protesting since July over endemic corruption, soaring joblessness and poor public services. Clashes erupted earlier this week, leaving several civilians and police dead. Prime Minister Haider al-Abadi has ordered an investigation into the violence which shows no sign of abating.

The violence prompted the temporary head of Iraq's parliament, the eldest lawmaker, to call an emergency meeting on Saturday to discuss the snowballing protests.

The newly-elected parliament earlier this week held its first session since the national elections in May. The session was adjourned amid disagreements as two blocs, both claiming to hold the most seats, vied for the right to form a new government.

The new parliament faces the twin tasks of rebuilding the north of the country following the war against the Islamic State group and rehabilitating services in the south, where severe water and electricity shortages have fueled protests.

A coalition led by al-Abadi and populist cleric Moqtada al-Sadr has the support of the U.S. and Saudi Arabia, while an alliance between former Prime Minister Nouri al-Maliki and militia leader Hadi al-Amiri has the backing of Iran.

Both alliances are dominated by Shiites, who have held the preponderance of power in Iraq since Saddam Hussein's ouster in 2003. But the largest Sunni blocs are aligned with al-Abadi and al-Sadr. Iraq's two main Kurdish parties have not taken a side.

A representative of the Shiite community's spiritual leader, the Grand Ayatollah Ali al-Sistani, condemned during the Friday prayers sermon the violence against peaceful protesters and called for the quick formation of a new government that can deal with the challenges facing the country.