Friday's anti-government rallies left 42 dead across the country.
"Hundreds of protesters spent the night in Tahrir Square and did not withdraw despite calls from security forces," an Interior Ministry source told Efe news.
Security forces were deployed in the streets adjacent to the central square, but life continues normally in the rest of Baghdad's neighbourhoods, according to the source.
Iraqis on Friday resumed rallies that first erupted in early October to call for better basic services and employment and protest corruption.
A total of 158 were killed in those early protests, mainly due to the police repression.
The new wave of protests has also left 2,312 people injured in clashes between security sources and demonstrators, according to Ali al Bayati, a member of the governmental Iraqi Commission for Human Rights.
Nearly 50 government buildings and parties' headquarters were damaged, according to the most recent figures.
Security forces were among the casualities, the Interior Ministry said, adding that some of them were victims of live ammunition and stone throwing by protesters.
The Ministry, meanwhile, denied that security forces have used real ammunition or excessive force against protesters.
It also stressed its respect for the peaceful protests.
The protests came days after influential Shia cleric Muqtada al-Sadr said that people had the right to take to the streets on October 25 if they wanted.
( With inputs from IANS )