Protesters complain of widespread corruption, a lack of job opportunities and poor basic services. In Baghdad, security forces opened fire on protesters marching in downtown's Rashid street.
Iraq's main port reopened on Thursday after being blocked by protesters for five days, while in Baghdad, four protesters were shot dead while trying to remove security barriers in a major central street, security and medical officials said.
At least 24 others were wounded as security forces fired live rounds and tear gas to disperse the protesters, security and medical officials said. They spoke on condition of anonymity in line with regulations.
In Baghdad, security forces opened fire on protesters marching in downtown's Rashid street, where the central bank is located, as they tried to remove barriers near two bridges that lead to the west bank of the Tigris river. Demonstrators have been trying to reach the Green Zone on the other side, which houses government offices and foreign embassies.
Tens of thousands of people have taken to the streets in recent weeks in the capital and across the Shia south to demand sweeping political change. The protesters complain of widespread corruption, a lack of job opportunities and poor basic services, including regular power cuts despite Iraq's vast oil reserves. More than 250 people have been killed since October 1.
Protesters have blocked roads to raise pressure on the government. A similar tactic is being used in Lebanon's ongoing anti-government demonstrations.
The reopening of Umm Qasr port, which houses a vital oil terminal and is an entry point for food and basic goods, came a day after the military called on the protesters to stop blocking roads and ports. It said the blockages had cost Iraq $6 billion and vowed to arrest those responsible.
Iraq's leaders have promised reforms and early elections, but the process they laid out could take months, and the protests have only grown in recent days.
Iraq has held regular elections since the overthrow of Saddam Hussein following the US-led invasion of 2003, but they have been dominated by Shia parties that have failed to deliver on promises to improve daily life.
The protests pose the biggest challenge to the government since it declared victory over militants from Daesh nearly two years ago.