Iraqi security forces opened fire on thousands of demonstrators who defied a curfew in Baghdad on Thursday and exchanged fire with gunmen in a southern city, killing two people on the third day of nationwide anti-government protests.

The protests, in which at least 20 have now been killed and over 600 wounded, began over unemployment and poor services but have escalated into calls for a change of government and pose one of the worst security challenges in years.

They appear to be independent of any political party and seemingly took the security forces by surprise.

“The bullets do not scare us. They do not scare Iraqis. This will all come down over their heads,” said one protester in the capital. At least 4,000 protesters gathered in Baghdad’s Tayaran Square and attempted to march onto the central Tahrir Square only to be met with open fire and heavy tear gas.

Police used live ammunition in the Zaafaraniya district of Baghdad, where a protester was shot dead, and there were protests in the northwestern Shula district. Police said protesters had fired at them in the town of Rifaen.