The military called on the protesters to stop blocking roads and ports, saying they had cost Iraq $6 billion, and it vowed to arrest those responsible. The U.S. Embassy urged the government to "engage seriously and urgently" with the demonstrators and condemned attacks on them.
Tens of thousands of people have taken to the streets in recent weeks in the capital and across the Shiite 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.
The protesters have focused their anger on Shiite political parties and militias, many of which have close ties to Iran . Across the south, they have attacked party and militia headquarters, setting some of them ablaze.
In the Shiite holy city of Karbala, protesters attacked the Iranian Consulate earlier this week, hurling firebombs over its walls. Security forces killed at least three people as they dispersed the protest. Days earlier, masked men suspected of links to the security forces opened fire on a demonstration there, killing at least 18 people.
Overnight, at least two protesters were killed in clashes with security forces near the provincial headquarters in the city, according to a protester and a medic who spoke on condition of anonymity for fear of repercussions.
In Baghdad, protesters clashed with security forces on a fourth bridge over the Tigris River after previous clashes forced the closure of three other spans, paralyzing much of the city. The protests have been centered in Tahrir Square, on the eastern bank of the Tigris, and the demonstrators have been trying to reach the Green Zone, which houses government offices and foreign embassies on the other side of the river.
As protesters moved toward the Martyrs' Bridge, north of the other three, they passed near the central bank. Iraqi security forces were deployed in large numbers around the bank and evacuated employees, but the protesters did not target the building.
Security and medical officials said at least 29 people were wounded after being hit with batons or exposed to tear gas on or near Martyrs' Bridge. They said a medic was killed near the Al-Ahrar Bridge, which has seen heavy clashes in recent days, and another was wounded. They spoke on condition of anonymity in line with regulations.
In Tahrir Square, family and friends called for the release of Siba al-Mahdawi, a 37-year-old activist and volunteer medic who was abducted over the weekend. Her brother, Ahmed al-Mahdawi, said she was taken by masked men dressed in black as she returned home from a protest Saturday. He said the family has received no word of her whereabouts since she vanished four days ago.
"She assumed responsibility for the family after our father died," he said, adding that she had taken care of her mother and four younger siblings as they struggled to find steady work. The U.S. Embassy in Baghdad called on the government to "engage seriously and urgently with Iraqi citizens who are demanding reform."
"We deplore the killing and kidnapping of unarmed protesters, threats to freedom of expression, and the cycle of violence taking place," it said. "Iraqis must be free to make their own choices about the future of their nation."
Maj. Gen. Abdul-Karim Khalaf, a spokesman for the armed forces, said the roadblocks and the protesters' blockade of the key port of Umm Qasr on the Persian Gulf had cost the country $6 billion. He said security forces are not using live ammunition but would arrest anyone trying to block roads or bridges.
Umm Qasr, which houses a vital oil terminal and also is an entry point for food and basic goods, has been blocked for five days. Clashes broke out when security forces tried to reopen it Tuesday, with one protester killed and eight wounded.
Security forces have killed at least 273 protesters in two major waves of demonstrations since early October, including four who died Wednesday of injuries suffered earlier. 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 U.S.-led invasion of 2003, but they have been dominated by Shiite Islamist 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 the Islamic State group nearly two years ago.
Internet access remained limited Wednesday after the government shut it down earlier this week. Netblocks, a civil society group that tracks internet restrictions, said usage dropped to 19% of normal levels overnight Tuesday before being partially restored.
Netblocks said Wednesday that Iraq "remains largely offline." It said an earlier series of internet outages during protests last month had cost the country more than $1 billion.
Krauss reported from Beirut.