Protesters warned of more action if their demands for political reforms are not met.
Tensions remain across Iraq, with I-S claiming responsibility for a deadly suicide bombing that's killed at least 32 people.
A funeral procession through the streets of Samawa as another deadly bomb blast leaves scores dead and injured.
The self-proclaimed Islamic State group has claimed responsibility for the two suicide car bombs, detonated near a government building and a bus stop in the Southern Iraqi city.
Further north in the capital Baghdad, protesters have ended their two-day sit-in after storming the city's Green Zone, home to ministries and foreign embassies.
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A rally spokeswoman told the crowd they will leave from a position of strength, and can return if nothing is done to stamp out government corruption.
"If this demand is not met, the people would then use all legitimate means that begins with storming the headquarters of the three executive branches or civil disobedience or going on strike."
Chanting "all politicians are thieves", hundreds of followers of the powerful Shiite cleric, Moqtada Al-Sadr, had invaded the parliamentary precinct.
Demonstrator Abdul Kudhair Al Abadi was reflecting the mood of the protest.
"We have been deprived from our rights for the past thirteen years; we have no rights whatsoever. I say to the corrupt: reforms or else! There is no place for you among us any more."
The Iraqi Parliament Speaker, Salim Al-Jabouri, has urged the country's political parties to act.
"If we reach a deadlock in doing reforms, then all options in this regard are open as long as such options will help end the crisis and serve Iraq. So I call on all political blocs to clarify their stance and present essential solutions for reforms."
Analysts have warned Baghdad risks descending into chaos.
President of the Middle East Research Institute, Dlawer Ala-Aldeen, says this may strengthen the hand of those pushing for Kurdish independence.
"The pressure is coming from outside. The Americans, the Iranians, the Turks, everybody is insisting on the Kurdish leaders to remain within the boundaries of Iraq, but in the meantime they are not offering them any alternative or any vision or any leadership forward. The main incentive for the international community has been, they are so focused on ISIS and defeating ISIS, they are trying to keep Iraq united. But Baghdad is not helping and the Kurds may well end up making their own decision."
