A hospital and local authorities in the southern Iraqi city of Najaf say four people were killed in unrest that erupted as a mall burned down during a demonstration there.

The Najaf province's security command said security forces arrested five mall guards who had fired at the demonstrators, killing and wounding several.

The city's Hakim Hospital said on Thursday morning that 17 people were also wounded in the unrest overnight.

The fire at the Bashir Mall erupted after the guards opened fire at supporters of populist Shiite cleric Moqtada al-Sadr who were rallying against his former aide, Kazm al-Issawi, outside the mall.

Al-Sadr had earlier condemned corruption in the country and fired al-Issawi over graft. His political office says the demonstrators were protesting against corrupt officials.