Iraq's government indefinitely postponed a much-anticipated national reconciliation conference on Sunday as at least 83 people were reported dead in a two-day spree of sectarian revenge killings and insurgent bombings.

The U.S. military reported the deaths of a Marine and four soldiers.

A brief statement from the Ministry of State for National Dialogue said only that the Iraqi political powers conference planned for Saturday had been put off because of "emergency reasons out of the control of the ministry."

The failure to bring Iraq's deeply divided politicians together appeared likely to exacerbate Prime Minister Nouri al-Maliki's attempts to strengthen political consensus, underscoring the effect worsening violence is having on efforts to stabilize the U.S.-backed government and curb the bloodshed.

CountryWatch: Iraq

Weekend revenge killings among Shiites and Sunnis left at least 63 people dead in a city north of Baghdad, while 11 people died Sunday in a series of apparently coordinated bombings on a girls school and other targets in the northern city of Kirkuk, where Kurds and Arabs are in a tense struggle for control of the oil-rich city.

Even by Iraq's bleak standards, October has been an especially bloody month. Hundreds of Iraqi's have died in attacks and 54 U.S. military personnel have been killed in the first two weeks alone.

U.S. commanders say that based on the record of past years, they expect a further spike in bloodshed throughout the Islamic holy month of Ramadan. Some Islamic militants believe that dying in combat during Ramadan brings extra blessings in paradise.

The tit-for-tat sectarian killings began late Friday with the discovery of the decapitated bodies of 17 Shiites kidnapped earlier in the day near Balad, a predominantly Sunni region northwest of Baghdad and a hotbed of the insurgency battling U.S. and Iraqi forces.

Suspected Shiite militiamen then began targeting Sunnis in Balad and surrounding towns, killing at least 46 overnight, according to police and hospital officials.

Extra police flooded into the area, 80 kilometers (50 miles) north of Baghdad, to enforce a curfew and additional security measures were taken in other villages in the area, Interior Ministry spokesman Brig. Abdul-Karim Khalaf said.

Despite that, bullet-ridden bodies continued to be delivered to the Balad's main hospital well into Sunday morning, according to a hospital director who asked that his name not be used for fear of reprisals.

An army officer in the nearby city of Tikrit confirmed the death toll and said 63 suspects — both Sunnis and Shiites — were arrested.

The Iraqi Islamic Party, the country's largest Sunni political group, said 30 Sunnis had been killed and accused the Shiite-dominated police force of cooperating with the militias in snatching 70 people from Balad hospital and other locations.

"The Iraqi Islamic party condemns the violence in Balad for which we hold the occupation forces and government fully responsible," the party said in a statement, using its standard term for the U.S. military presence.

The bombings in Kirkuk, 290 kilometers (180 miles) north of Baghdad, appeared part of an increasingly bloody power struggle between Arabs and Kurds for control of northern Iraqi oil wealth that has undermined U.S. hopes of stabilizing the region.

Two girls who died when a man detonated explosives strapped to his body in front of the Kurdish al-Mallimin girls high school in downtown Kirkuk, police officials said.

Distraught mothers sobbed and beat their chests while awaiting word of their daughters, while fire fighters doused cars set alight by the blast and Iraqi police joined by U.S. troops sought to keep order. The powerful explosion left a sizable crater in the concrete road in front of the school.

Five others died when a suicide bomber at the wheel of an explosives-rigged vehicle targeted a convoy of the Facilities Protection Service that guards government buildings and infrastructure. Ten others were wounded in that attack, according to police Brig. Sarhat Abdul-Qadir.

Three other people were killed and eight injured when a suicide bomber blew himself up in a market in the southern section of the city, Abdul-Qadir said. Associated Press Television News cameras filmed pools of blood on the ground around the market while firefighters struggled to break into shops where fires were raging.

Two other car bombs around the city killed one other person and injured at least five, Abdul-Qadir said.

The American military said the Marine was killed in combat in Anbar province, the Sunni heartland west of Baghdad on Saturday.

Three soldiers died in a roadside bombing Saturday south of Baghdad, and one soldier was killed in a roadside bombing Friday night southwest of the capital. The soldiers' names were being withheld pending notification of their families.

In Baghdad Sunday, Interior Ministry undersecretary Hala Shakir Salim survived a roadside bomb attack that killed seven others, the latest government official targeted in a campaign by insurgents to undermine the U.S.-backed government.

Four bystanders and three bodyguards were killed in the blast that hit as Salim was being driven to work from her home in Baghdad's eastern Mustansiriya neighborhood, police Capt. Mohammed Abdul-Ghani said. Salim is the chief financial officer for the ministry, which runs the Iraqi police forces.

A husband, wife and two of their sons were killed and two daughters-in-law critically wounded Sunday morning when gunmen burst into their home in Mosul, Iraq's third largest city 360 kilometers (225 miles) northwest of Baghdad. Police Col. Eid al-Jibouri said the identities of the attackers and their motive were unknown.

South of Baghdad, three women and four men were killed in drive-by shootings in the predominantly Shiite village of Wahda on Saturday afternoon, according to provincial police spokesman Lt. Hadi Hassan.

Two policeman were killed in attacks by unidentified gunmen in the northern city of Mosul and in Suwayrah, 40 kilometers (25 miles) south of Baghdad, police spokesmen said.

A suicide bomber apparently targeting plain clothes policemen blew himself up in the city of Tal Afar 420 kilometers (260 miles) northwest of Baghdad, killing an eight-year-old and wounding six others, Najim Abdullah, the provincial governor said.

A bomb also exploded Sunday morning in the old bazaar in the southern city of Basra, injuring 3 people, police Capt. Karim al-Zaidi said.

Also Sunday, the U.S. military announced Iraq's Central Criminal Court had sentenced an al-Qaida member to death and convicted 64 others on charges of belonging to armed groups and other crimes, the U.S. military command said Sunday.

The military's statement did not name the man condemned to death, but said he was a "known member of the al-Qaida organization." Others sentenced to life in prison included a Saudi Arabian man that the court said had admitted to coming to Iraq to fight U.S. and government forces.