Prime Minister Nouri al-Maliki met with Grand Ayatollah Ali al-Sistani in Najaf.
BAGHDAD, Iraq -- Iraq's most influential Shiite cleric on Saturday warned the prime minister to quell violence or risk "other powers" filling the gap, while police found the tortured and blindfolded bodies of 13 Pakistani and Indian pilgrims and their Iraqi driver.
At least 15 violent deaths were reported elsewhere in Iraq, while the government announced it had formally taken over the notorious Abu Ghraib prison from coalition authorities.
Prime Minister Nouri al-Maliki met with Grand Ayatollah Ali al-Sistani in Najaf, 100 miles south of Baghdad, the cleric's office said. In July, al-Sistani was credited with restraining the Shiite community from widespread retaliation against minority Sunnis following horrific attacks on Shiite civilians.
"If the government does not do its duty in imposing security and order to the people and protecting them, it will give a chance to other powers to do this duty and this a very dangerous matter," al-Sistani's office quoted him as saying.
The meeting came two days after a barrage of coordinated attacks across mainly Shiite eastern Baghdad killed 64 people and wounded 286. The prime minister's office said in a statement that 17 suspects had been arrested after the bombings, but gave no further details.
Hundreds of Iraqis have been killed in violence this week, despite a massive security operation in the capital involving an extra 12,000 Iraqi and U.S. troops that has targeted some of Baghdad's most problematic neighborhoods.
In Washington, a day after a Pentagon report described spreading sectarian violence, President Bush painted a rosier picture.
"Our commanders and diplomats on the ground believe that Iraq has not descended into a civil war," Bush said in a radio address, although he acknowledged "a bloody campaign of sectarian violence" and the "difficult and dangerous" work of trying to end it.
Authorities, meanwhile, canceled a highly anticipated ceremony in which Iraq's Defense Ministry was to assume operational control of the country's armed forces command from the U.S.-led coalition. No new date was set for the event.
Lt. Col. Barry Johnson, a U.S. military spokesman, originally said the delay was due to "miscommunication" between coalition forces and the Iraqi Ministry of Defense regarding the timing of the ceremony.
Johnson said later that it had become "apparent" that part of the miscommunication had been about the wording of the document "delineating" the responsibilities of the joint headquarters and the coalition's role in supporting their efforts.
Handing over control from the coalition to Iraqi authorities is a key part of any eventual drawdown of U.S. troops in the country.
In the latest violence, police said Saturday that a group of pilgrims -- 11 Pakistanis, including five women, and two Indians -- and their Iraqi driver were ambushed and killed on their way to the Shiite holy city of Karbala, 50 miles south of the capital.
The bodies, blindfolded and with hands and feet bound, all bore signs of torture, an official at Karbala morgue said. The official, who spoke on condition of anonymity for fear of reprisals, said the 14 had been dead for three days and their bodies had been found on Friday.
Shiite pilgrims are to observe Shaaban, a mid-month religious celebration, on Sept. 9.
Pakistan on Saturday condemned the killings and urged its citizens to postpone travel to Iraq.
Tensions also brewed in the north Saturday, with a leading Sunni politician slamming a decision by Kurdistan president Massoud Barzani ordering the Iraqi national flag to be replaced with the Kurdish one in his northern autonomous region.
The move has troubled Sunni Arabs, who fear Kurds are pushing for secession under the nation's new federal system.
Sunni Arab lawmaker Saleh al-Mutlaq said there was no problem with the Kurds "keeping the land that's within their acknowledged borders," but he said that lowering the Iraqi flag "is definitely disturbing for us and any patriotic individual in Iraq."
A spokesman for the Kurdistan government defended his government's decision to remove the Iraqi flag.
"We consider that this flag represents the ideology of the Baath Party" of Saddam Hussein, Khalid Saleh told The Associated Press. "And this regime has collapsed."
Separately, the Chaldean Patriarch of Baghdad said Saturday he had spoken on the phone with the Rev. Hanna Saad Sirop, who is director of the Theology Department at Babel College and was kidnapped in Baghdad on Aug. 15.
Patriarch Emmanuel Delly told the Italian missionary news agency MISNA that the kidnappers had assured him at the end of his conversation last Saturday that they would release the priest immediately, but he had heard nothing since.
In other violence, according to police:
-- A car bomb exploded near a police station, killing three civilians and wounding 14, in Mahaweel, about 35 miles south of Baghdad.
-- A car bomb exploded in the Baghdad neighborhood of Waziriyah -- which is among those to be included in the expanded security operation -- as a police patrol passed by, followed by a roadside bombing later at the same site, killing three people.
-- Police found the bodies of five women dumped in three locations in central Baqouba, 35 miles northeast of Baghdad.
-- Gunmen killed three policemen at a Baqouba bus station.
-- A mortar round struck a fuel station in Mahmoudiyah, 20 miles south of Baghdad, killed one person.
Associated Press writers Rawya Rageh, Rebecca Santana and Qais al-Bashir in Baghdad contributed to this report.