Security forces killed a protester and wounded 91 others in Baghdad on Saturday, security and medical sources said, as tens of thousands of Iraqis gathered in mass anti-government protests in the capital and blocked roads leading to a major port.

Protesters have been gathering in the capital's central Tahrir Square for weeks, demanding the fall of the political elite in the biggest wave of mass demonstrations since the fall of Saddam Hussein in 2003.

Protests have accelerated dramatically in recent days, drawing huge crowds from across sectarian and ethnic divides. More than 250 people were killed in October.

Clashes have focused on the ramparts to the Republic Bridge leading across the Tigris to the heavily fortified Green Zone of government buildings, where the protesters say out-of-touch leaders are holed up in their walled-off bastion of privilege.

Security forces on Saturday erected concrete walls on one of Baghdad's main streets, which leads into Tahrir Square in an attempt to reduce the turnout but a spontaneous protest in which crowds surrounded soldiers driving bulldozers forced them to take the structures down.

"Take it down, take it down," they chanted.

The protests, driven by discontent over economic hardship and corruption, have broken nearly two years of relative stability in Iraq.

Thousands of protesters were blocking all roads leading to Iraq's main Gulf port Umm Qasr near the oil-rich city of Basra after security forces used live rounds and tear gas overnight.

Operations at the port, which receives the vast bulk of Iraq's imports of grain, vegetable oils and sugar, have been at a complete standstill since Wednesday. On Friday, both the teachers' and lawyers' unions said they would extend strikes they declared last week. Schools had been due to reopen on Sunday after a week of canceled classes.

Many see the political class as subservient to one or another of Baghdad's main allies, the United States and Iran, who use Iraq as a proxy in a struggle for regional influence.

"We don't want anyone interfering in our affairs, not Saudi Arabia, not Turkey, not Iran, not America. It's our country, our demands are clear," said protester Ahmed Abu Mariam.

(With input from Reuters)