Security forces in Iraq have opened fire on protesters in Baghdad, killing and wounding several people, according to witnesses, the latest bout of bloodshed amid ongoing protests demanding an overhaul of the country’s political system.

Al Jazeera’s Natasha Ghoneim, reporting from Baghdad, said the clashes on Monday occurred when protesters tried to scale barricades on Baghdad’s Ahrar Bridge.

“A witness told us that the police responded with live ammunition, not tear gas, and that at least five people may have been killed,” she said. “A medical source told us about 30 people have been injured and these injuries are gunshot wounds to the head and face. The injured include security forces as well as protesters.”

A spokesperson for Iraq’s Prime Minister Adel Abdul Mahdi disputed the claims however, telling Al Jazeera that “no one has been killed [in Baghdad] this evening”.

The Reuters news agency also said at least five people were killed in the clashes near the Ahrar Bridge. Video footage showed security forces shooting one protester dead with live ammunition, it said, while a Reuters cameraman said he saw at least four other people killed.

However, security and medical sources told the agency that one person died and 22 were wounded. The sources said rubber bullets and tear gas, not live ammunition, were used.

The Associated Press also reported clashes in Baghdad, saying the violence occured after anti-government protesters crossed the Ahrar Bridge and broke into the city’s fortified Green Zone, where the prime minister’s office and other government buildings are located.

The protesters hurled rocks and set tires and dumpsters ablaze, sending clouds of black smoke into the air, the agency said. Security forces then flooded into the area to protect government buildings, and gunfire echoed through the streets.

Police and hospital officials quoted by AP said at least five demonstrators and a member of the security forces were killed.

Monday’s deaths were in addition to three protesters who were killed late on Sunday when security forces opened fire on a crowd trying to storm the Iranian consulate in the Shia Muslim holy city of Karbala, security and medical sources said.

Security forces in Baghdad had refrained from using live fire in recent days. Nearly 150 people were killed between October 1-7, with 70 percent of deaths resulting from bullets to the head or chest, a government committee report has found.

Scores more have been killed since protests resumed on October 24.

The demonstrations are rooted in long-standing grievances over poor governance, official corruption and lack of economic opportunity, but have since expanded into demands for sweeping changes and an overhaul of the country’s political system, which was established after the US-led invasion in 2003.

Demonstrators have directed their ire at a class of elite leaders whom they accuse of pillaging the oil-rich country’s wealth while the population grows poorer. Protesters have also directed their rage at neighbouring Iran and the powerful Iraqi Shia militias tied to it.

Undeterred by the latest violence, protesters pushed on Monday with civil disobedience tactics they have increasingly adopted over the past week, including sit-ins, road closures and strikes.

The national teachers’ syndicate shut down schools across the country, and other trade unions later joined in. Government offices in more than a half-dozen southern cities have been either stormed or closed for lack of staff, with demonstrators hanging banners reading “Closed by order of the people” in front of the buildings.

Others have erected checkpoints to stop security forces or imposed curfews on officials and police, with roads cut in Samawa and protests in Nasiriyah and Hillah on Monday. Protesters have also shut the highway to the Umm Qasr port, one of the main conduits for food, medicine and other imports into Iraq.

In Amara, sit-ins were underway on Monday at the Halfaya and Buzurgan oil fields, blocking employees from accessing the site but not interrupting production.

The spreading non-violent actions defied a plea the previous evening by the embattled prime minister for protesters to end their campaign.

Abdul Mahdi, in a statement late on Sunday, called on protesters to halt the sit-ins, saying the “blocking roads leading to Iraq’s ports is causing big losses exceeding billions of dollars”.

His statement made no mention of resignation, despite Iraqi President Barham Salih saying on Thursday that Abdul Mahdi was willing to step down once political leaders agreed on a replacement.

Salih had also called for new election law and said he would approve early elections once it was enacted. In a meeting with the heads of trade unions on Sunday, the president said the new election law would be submitted to parliament this week.

However, even if the new electoral law is quickly approved, the process of holding elections and forming a new government could take several months.