Rockets were fired at Baghdad's Green Zone Saturday after Iraq's most violent protest in years saw seven people killed in clashes between police and demonstrators advancing on the fortified area.

The body coordinating security operations in Iraq said several Katyusha-type rockets were fired from within Baghdad at the Green Zone, which houses most of the country's key institutions.

"Several Katyusha rockets fired from the Baladiyat and Palestine Street areas landed in the Green Zone," the Joint Operations Command said in a statement, without specifying who fired them.

Police and interior ministry officials confirmed to AFP that several rockets were fired at the area but could not specify what the presumed target was nor whether there were any victims.

"Several rockets, maybe six or seven, struck the Green Zone. I can hear the siren is being sounded in the area," Maysoon Damaluji, a lawmaker who lives in the protected area, told AFP.

A diplomat who also lives in the Green Zone said he heard four blasts.

Several main roads were closed and extra security was deployed across Baghdad late Saturday.

The Green Zone is a vast area in central Baghdad that houses the prime minister's office, the presidency, parliament and several major embassies, including the huge US mission.

Although it could not be ascertained that both events were linked, it also shelters Iraq's electoral commission, whose replacement was a key demand of the thousands of protesters in the city earlier Saturday.

The rally, mostly attended by supporters of cleric Moqtada Sadr, started peacefully but some protesters subsequently broke away and attempted to force their way past a police cordon to reach the Green Zone.

- Deadly protest -

Security forces posted on a bridge over the Tigris River used tear gas and rubber-coated bullets to repulse the protesters.

"There were seven dead as a result of the violence. Two of them are from the security forces and the other five are protesters," a police colonel told AFP on condition of anonymity.

He said more than 200 were hurt in the chaos. Most were protesters suffering from tear gas inhalation, but at least 11 had more serious injuries caused by bullets and tear gas canisters.

Sadr supporters accusing Iraq's political class of corruption and nepotism broke into the so-called Green Zone twice in 2016, storming the prime minister's office and the parliament building.

Saturday's demonstrators received a de facto green light to escalate their protest in the shape of a statement from the Najaf-based Sadr.

"If you want to approach the gates of the Green Zone to affirm your demands and make them heard to those on the other side of the fence... you can," he said.

Sadr, a mercurial Shiite who once led a rebellion against US occupation but has more recently spearheaded an anti-corruption protest movement, eventually called for restraint but warned Prime Minister Haider al-Abadi not to turn a deaf ear.

"I urge him to deliver those reforms immediately, listen to the voice of the people and remove the corrupt," he said in a statement.

Abadi said the violence would be investigated and those responsible for it prosecuted.

The protest, the latest in a series across the country over the past few days, was focused on demands for electoral reform ahead of provincial polls slated for September.

- Partisan commissioners -

"Our action will get tougher, even if that involves physically taking over the commission," Abu Haidar, a protester wearing traditional Arab dress, told AFP before the rally turned violent.

The electoral commission issued a statement asking for protection from the premier's office and the international community.

The protesters want the members of the electoral commission to be replaced, on the grounds that they are all affiliated to political parties and that the body supervising nationwide ballots was therefore anything but independent.

They also want the electoral law to be amended to give wider representation to smaller parties in the country's elected bodies.

Sinan al-Azzawi, a popular Iraqi actor, was among those who addressed the protest before the violence broke out.

Politicians "are profiteers and their only loyalty is to the countries they used to live in but not to Iraq", he said, referring to the Saddam-era exile of many of the country's current leaders.

"Those politicians, they created an electoral commission based on sectarian quotas. It has nine commissioners who belong to political entities... It's not independent," he said.