Dozens of fighters linked to Al-Qaeda in Iraq streamed into Shiite villages north of Baghdad on Sunday, torching homes and killing at least 15 people before Iraqi police and defiant residents drove them away, police and army officials said.

In all, at least 41 people were killed or found dead nationwide — including nine shot by security contractors in Baghdad, police said, and five who died when a booby-trapped bicycle exploded near a cafe serving tea and food during Ramadan fasting hours.

The bloodshed came the day after Al-Qaeda in Iraq announced a new offensive in the Islamic holy month and was a blow to government hopes that a peaceful Ramadan would demonstrate the success of the seven-month operation in the capital.

In the raids on the villages of Jichan and Ghizlayat, the fighters arrived from several different directions and residents fought back until Iraqi security forces arrived and chased the attackers, who fled to nearby farms.

The clashes about 60 miles north of Baghdad lasted about two hours, the officials and witnesses said. They spoke on condition of anonymity because they feared reprisals.

In Baghdad, Iraqi police said security contractors opened fire in a predominantly Sunni neighborhood of western Baghdad on Sunday, killing at least nine civilians. The U.S. Embassy said contractors working for the State Department were involved in an incident in Baghdad but provided no further details, saying an investigation was still under way.

"We saw a convoy of SUVs passing in the street nearby. One minute later, we heard the sound of bomb explosion followed by gunfire that lasted for 20 minutes between gunmen and the convoy people who were foreigners and dressed in civilian clothes. Everybody in the street started to flee immediately," said Hussein Abdul-Abbas, who owns a cell phone store nearby.

The police officer who reported the shootings in Mansour spoke on condition of anonymity because he was not authorized to release the information.

American soldiers arrived afterward and were not involved, military spokesman Lt. Col. Scott Bleichwehl said.

Many contractors have been accused of indiscriminately firing at American and Iraqi troops, and of shooting to death an unknown number of Iraqi citizens who got too close to their heavily armed convoys, but not one has faced charges or prosecution.

The wartime numbers of private guards are unprecedented — as are their duties, many of which have traditionally been done by soldiers. They protect U.S. military operations and have guarded high-ranking officials including Gen. David Petraeus, the U.S. commander in Baghdad. They also protect journalists, visiting foreign officials and thousands of construction projects.

The government, meanwhile, faced a deepening political crisis with Saturday's announcement that anti-U.S. cleric Muqtada al-Sadr's followers were withdrawing from the Shiite alliance in parliament. Al-Sadr's followers hold 30 of the 275 parliament seats.

The announcement, made to reporters in Najaf, means the Shiite-led government can count on the support of only 108 parliament members — 30 short of a majority. However, it could probably win the backing of the 30 independent Shiite parliamentarians, as well as some minor parties.

Al-Sadr's decision will sharpen the power struggle among armed Shiite groups in the south, which includes major Shiite religious shrines and much of the country's vast oil resources.

But Shiites have shown signs of increasing frustration with militia violence, much of it blamed on breakaway Mahdi Army factions and criminal gangs and extortion rings.

American commanders in southern Iraq have said Shiite sheiks are showing interest in joining forces with the U.S. military against extremists, in much the same way that Sunni clansmen in the western part of the country have worked with American forces against al-Qaida in Iraq.

One of those clansmen, Sheik Abdul-Sattar Abu Risha, was assassinated Thursday outside his compound in the Anbar capital of Ramadi, just days after he met with President Bush.

The U.S. military said an al-Qaida linked militant believed responsible for his death — Fallah Khalifa Hiyas Fayyas al-Jumayli, an Iraqi also known as Abu Khamis — was seized Saturday.

"We do not assess that he was operating alone, there is an investigation and continuing operations that are focused on ensuring that all people who were involved in this attack or in this murder will be detained," said Rear. Adm. Mark Fox, a U.S. military spokesman.