At least 20 demonstrators were killed and more than 600 others injured Tuesday when Iraqi forces attempted to break a protest camp in the southern city of Karbala, according to local media.
A security source earlier said anti-riot police moved to disperse "an unlicensed sit-in" in central Karbala.
He said protesters ignored calls by security forces to end their sit-in.
Earlier, Gaafar al-Saadi, an eyewitness, said hundreds of gunmen attacked the sit-in in central Karbala.
"They opened fire randomly while police vehicles rammed into protesters, leaving at least ten people dead," he told Anadolu Agency.
Alaa al-Sherifi, another witness, said ambulances were unable to move the injured in the first hours of the dispersal "due to heavy fire by security forces".
"This attack by security forces was totally unjustified," he said.
More than 100 people have been killed and more than 3,600 others injured since a second wave of protests began in several Iraqi provinces on Friday, according to human rights groups.
The first wave of protests in early October left 149 protesters and eight security personnel dead.
Anger has been building in Iraq in recent years due to rising unemployment and rampant corruption. Many people in the country have limited access to basic services such as electricity and clean water.
According to World Bank figures, Iraq's youth unemployment is around 25%. It is also ranked the 12th most-corrupt country in the world by several transparency organizations.
