At least five people have been killed and hundreds wounded since Tuesday in clashes between anti-government protesters and security forces in Iraq.
Thousands rallied in Baghdad, Nasiriya and other cities to protest at lack of jobs, poor services and corruption.
Social media platforms and internet access have been blocked in the capital and other parts of the country.
Blaming unnamed "rioters" for the unrest, the government vowed to address protesters' concerns.
An unconfirmed report by Reuters news agency says curfews have been imposed in Nasiriya and two other southern cites, Amara and Hilla.
The United Nations has called on the authorities to exercise restraint.
"Every individual has the right to speak freely, in keeping with the law," UN special representative Jeanine Hennis-Plasschaert said.
The protests, which appear to lack any organised leadership, are the largest since Prime Minister Adel Abdul Mahdi took office a year ago.
Three people were killed or died of their wounds on Wednesday, officials said, as the anti-government protests erupted for a second day and spread to more areas.
In the capital, police fired tear gas and live ammunition in an attempt to disperse demonstrations in several districts.
Protesters also attempted to reach central Tahrir Square, which police had earlier sealed off along with a nearby bridge leading to the Green Zone, where government buildings and foreign embassies are located.
Facebook, Twitter, WhatsApp, Instagram and other social and messaging apps were blocked by multiple internet providers from 15:30 (12:30 GMT), the Netblocks site reports.