Iraq's top Shia cleric on Friday denounced the murder and abduction of anti-government protesters, calling for weapons to be placed under the control of the state.
Around 460 people have been killed and 25,000 wounded, most of them protesters, since anti-government rallies erupted on October 1 in Baghdad and the Shia-majority south.
Since then demonstrators in the capital and southern cities have disappeared almost daily, in most cases taken from near their homes as they returned from protests.
"We strongly denounce the killings, abductions and attacks of all kinds that have been taking place," Grand Ayatollah Ali Sistani said in a sermon delivered by his representative in the shrine city of Kerbala during the weekly Friday prayer.
London-based rights group Amnesty International on Friday urged Baghdad to clamp down on what it called a "campaign of terror targeting protesters".
Protesters accuse pro-Iran armed factions of playing a role in the killings and abductions.
Sistani specifically mentioned an attack late last Friday, when unidentified gunmen stormed and torched a multi-storey building in Baghdad where protesters had camped out for weeks.
At least 20 protesters and four police officers were killed and about 80 demonstrators abducted, medical sources and witnesses said.
The revered Shia cleric also denounced Thursday's lynching by demonstrators of a teenager accused of attacking protesters in Baghdad, calling it "an atrocious crime".
Such actions "reaffirm once again the importance of what the marjaiyah (Shia religious leadership) has repeatedly called for and that is that all weapons must be placed under the control of the state", he said.
Sistani urged authorities to prosecute those responsible for the violence and called on protesters to keep their demonstrations peaceful.
Amnesty in its statements also called on Iraq's authorities "to step up to their responsibilities".
Iraq must "take immediate and effective action to put an end to a growing lethal campaign of harassment, intimidation, abductions and deliberate killings of activists and protesters," it said.
"The authorities' utter lack of action over the past weeks has paved the way for this horrifying new stage in what is clearly a full-on attempt to crush the protests in Iraq through instilling fear among the population," said Amnesty's Middle East Research director Lynn Maalouf.
She said government inaction indicated acquiescence and in some cases complicity in the "enforced disappearances, torture and unlawful killings of people who are on the streets to claim their human rights".