The anti-government demonstrations rocking the Iraqi capital and the Shiite-majority south since October had abated in recent weeks amid spiralling tensions between Iraq's key allies, the United States and Iran.

To recapture momentum and boost pressure on authorities, protesters this week began shutting down roads across the country -- but violence against them has escalated, too.

The young demonstrator was shot dead by unidentified assailants after he left the main protest camp in Basra, a security source said.

He had no papers on his person and police were waiting for someone to identify the body, the source told AFP.

It was the second straight night a protester was gunned down in Basra. Female activist and paramedic Janat Madhi, 49, was killed the same way late on Tuesday.

The deaths bring this week's toll to 12 demonstrators killed, according to the Iraqi Human Rights Commission, a state-funded monitor which reports on protest violence.

Four people were killed in Baghdad, one in Diyala, two in Karbala and five in Basra, including the latest two killings.

"Violence against demonstrators is clearly ongoing," commission member Ali Bayati told AFP.

"The unknown armed groups targeting protesters show that security forces are unable to protect citizens," he said.

Demonstrators have accused authorities of implementing a double standard, swiftly arresting anyone blocking roads with burning tyres while failing to apprehend those who have kidnapped and killed dozens of activists.

Hundreds of students gathered in Basra on Thursday morning to protest against the killings, chanting and holding up signs saying "Give us a country."

This week's violence brings to 470 the overall death toll since protests erupted in October, according to an AFP tally of reports from medical or security sources and the Human Rights Commission.