At least 18 people were arrested, security sources said later. There appeared to be no deaths. At least 27 people sustained tear gas-related injuries, medical sources said.

The second week of protests have begun in Iraq as demonstrators continue to demand the removal of the current regime, including the Prime Minister Adil Abdul-Mahdi.

On Wednesday, the Iraqi security forces fired tear gas and live rounds into the air to disperse protesters in central Baghdad as the biggest wave of anti-government demonstrations in decades spread out across the capital.

Chaotic scenes unfolded as the din of gunshots and stun grenades rocked the streets where groups of anxious young men - some heavily bandaged - ran from security forces, Reuters correspondents said. Tuk-tuks whizzed by ferrying protesters, some of them wounded.

Armored police vehicles blocked their path, turning most away. Policemen dragged a driver out of his tuk-tuk and beat him and a fellow rider with sticks before arresting them.

At least 18 people were arrested, security sources said later. There appeared to be no deaths. At least 27 people sustained tear gas-related injuries, medical sources said.

More than 260 Iraqis have been killed since the start of October in the largest demonstrations since the fall of Saddam Hussein in 2003. Protesters are demanding the overthrow of a political class seen as corrupt and beholden to foreign interests.

Protesters had begun trying to block bridges earlier this week as part of efforts to bring the country to a standstill, with thousands joining anti-government demonstrations in the capital and southern provinces. Security forces killed at least five people on Monday during one such attempt.

On Wednesday, the usually bustling surrounding streets were empty, with most shops shuttered.

“We are peacefully protesting,” said Abu Zahra, 50. “We are here to block the bridges. If we don’t, security forces are going to retake all the bridges and Tahrir Square, and end our protest. We are defending our brothers in Tahrir.”

Thousands of people had been gathering for weeks in central Tahrir Square. Clashes over two other bridges near the square have taken place regularly, bringing the total of blocked bridges to five.

“Blocking roads and bridges is illegal sabotage. Security forces have strict orders not to use live ammunition against protests and they are adhering to the rules of engagement but this could change,” the prime minister’s spokesman said.

In the 24 hours to late Tuesday, security forces shot dead at least 13 protesters.

Thousands have also demonstrated in Iraq’s impoverished southern Shi’ite heartland.