Shafaq News / Katyusha rockets landed in the Green Zone on Tuesday, a security source reported.

The source told Shafaq News agency that the U.S. embassy sounded sirens following the attack.

No further details were disclosed.

Mortar shells landed yesterday near one of the Joint Operations Command's headquarters and the vicinity of the U.S. embassy in the Green Zone, Baghdad, a security source reported.

Heavy clashes erupted in Baghdad, killing and injuring dozens of civilians and members of the Security forces, after powerful Shi'ite cleric Muqtada al-Sadr said he would quit politics, prompting his loyalists to storm a government palace and fight with rival groups.

As night fell, machine-gun fire and explosions rang out, with tracer fire rising into the sky above the Green Zone that houses government headquarters and foreign embassies, in the worst fighting the Iraqi capital has seen in years.

It followed a day of violence prompted by Sadr's announcement that he would withdraw from all political activity - a decision he said was in response to the failure of other Shi'ite leaders and parties to reform a corrupt and decaying governing system.

Sadr later said he was staging a hunger strike in protest against the use of weapons by all sides.