Protesters have stormed the Iranian consulate in the southern Iraqi city of Basra and started a fire inside as part of ongoing demonstrations that have turned deadly in recent days.

At least 10 protesters have died in clashes since Monday, including three who were shot dead by security forces on Thursday night as protesters hurled Molotov cocktails and set fire to a government building and the offices of Shia militias in the city.

Residents of Basra and other cities in Iraq’s oil-rich southern Shia heartland have been protesting since July over endemic corruption, soaring joblessness and poor public services.

The prime minister, Haider al-Abadi, has ordered an investigation into the violence, which shows no sign of abating. Iraq’s parliament will hold an emergency session on Saturday.

Protesters shouted anti-Iran slogans outside the Iranian consulate on Friday evening before storming it and starting a blaze. Smoke could be seen rising from the building. Protesters also burned an Iranian flag.

Many residents accuse Iranian-backed political parties of interfering with Iraqi politics, and some hold them responsible for mismanagement and poor services in the city.

In Baghdad, security forces launched a search operation to try to determine the source of three mortar shells that landed inside Baghdad’s heavily fortified Green Zone. There was no immediate claim of responsibility for the shells, and no casualties were reported.

The newly elected parliament held its first session this week 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 government.

MPs face the twin tasks of rebuilding the north of the country after the war against Islamic State and rehabilitating services in the south, where there are severe water and electricity shortages.

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

Both alliances are dominated by Shias, who have held the preponderance of power in Iraq since Saddam Hussein was ousted in 2003. The largest Sunni blocs are aligned with Abadi and Sadr; Iraq’s two main Kurdish parties have not taken a side.

During Friday prayers, a representative of the Shia community’s spiritual leader, the Grand Ayatollah Ali al-Sistani, condemned the violence against protesters and called for the quick formation of a government to deal with the challenges facing the country.