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A homicide car bomber struck as worshippers were leaving a Shiite mosque in a northern Iraqi town Friday, the Muslim day of prayer, killing at least 12 people. Militants killed 12 other people across the country as the Sunni-dominated insurgency pressed its "all-out war" to destabilize the country.

The 24 deaths came during a third day of mayhem in which nearly 200 people were killed in bombings, mostly in Baghdad (search). More than 600 have been wounded in the stunning rampage by insurgents, including Al Qaeda in Iraq.

The bombing at the Hussainiyat al-Rasoul Mosque (search) in Tuz Khormato, 130 miles north of Baghdad, killed 12 people and wounded 21, said police Col. Sarhat Qader.

Police subsequently captured a young man wearing a homicide bomb belt and heading toward a second mosque in Tuz Khormato. Authorities said the man identified himself as Muhammed Ali, a Saudi citizen.

In other violence, gunmen opened fire on day laborers in the capital, killing three and wounding a dozen.

"We are innocent people ... Those criminals and terrorists came and did this to us," said Salah Aziz Ali, one of the wounded.

On Thursday, homicide bombers killed at least 31 people in three attacks targeting Iraqi police. A day earlier, at least 167 people were killed and 570 wounded in more than a dozen bombings in Baghdad. The largest single toll resulted from a homicide bombing against day laborers in the largely Shiite Kazimiyah (search) neighborhood in north Baghdad.

The U.S. military continued attacking militant strongholds in western Iraq along the Syrian border, where militants hold many towns and villages along the Euphrates River as it flows southeastward.

Al Qaeda in Iraq said the brutal bombings in Baghdad were reprisals for the joint Iraqi-U.S. operation that pushed insurgents out of their stronghold in Tal Afar, also near the Syrian border in Iraq's far north.

The American military said U.S. jets pounded an abandoned school used by Al Qaeda in the town of Karabilah, about 200 miles northwest of Baghdad. Nine insurgents were killed in Thursday night's strike.

Before dawn Friday, U.S. jets were called in again to destroy what the military said was a bomb factory in Haditha, also along the Euphrates in western Iraq.

Two days earlier, Al Qaeda in Iraq leader Abu Musab al-Zarqawi vowed to wage an "all-out war" on the country's Shiite majority, calling its members collaborators of the "Jews and Crusaders."

At Al-Kindi Teaching Hospital, where the laborers were taken after Friday's drive-by shooting, the wounded lined the corridors, while others lay on gurneys as doctors worked frantically to stanch bleeding and bandage wounds.

A car bomb also detonated near an Iraqi police patrol in Haswa, near Baghdad, killing three officers and wounding four, police Capt. Muthana Khalid said.

And in the Iskandariya district, 30 miles south of Baghdad, gunmen broke into the local mayor's house and shot him to death after first killing his four bodyguards, police Capt. Muthans Khalid said.

In the capital's Shiite district of Sadr City, gunmen assassinated Sheik Fadil al-Lami, the cleric at Imam Ali mosque, as he waited to fill his car with gas, said police Lt. Col. Shakir Wadi. Police also discovered the bodies of three people — including an Iraqi soldier — in the district, Wadi said.

The U.S. military also said Friday a Marine had been killed near Ramadi, the volatile capital of Anbar Province that stretches west from Baghdad to the Syrian, Jordanian and Saudi borders.

The spike in violence, U.S. and Iraqi officials said, was not surprising. It was viewed as a campaign by the Sunni-dominated insurgency to derail the political process and the Oct. 15 referendum on the draft constitution. Sunnis, once the power brokers under Saddam Hussein's regime, complain that the draft charter heavily favors Iraq's Shiite and Kurdish populations.

"These spikes of violence are predictable around certain critical events that highlight the progress of democracy," said Maj. Gen. Rick Lynch, the chief American military spokesman.

Lynch said the joint Iraqi-American force of 8,500 killed 145 insurgents and captured 361 in the second operation in a year to rid Tal Afar of militants, including foreign fighters crossing from Syria.

Iraqi and U.S. officials say the fighters sneak across the porous border and accuse the Damascus government of doing little to stop the influx. While Syria has repeatedly denied the charges, Iraqi officials have adopted an increasingly stronger tone, and the country's defense minister has pledged that operations targeting the militants would be extended to other Euphrates River valley towns seen as militant safe havens.

"We will not retreat or be silent. There will be no room for you (insurgents) in all of Iraq. We will chase you wherever you go," Defense Minister Sadoun al-Dulaimi, a Sunni, told reporters.

While the overwhelming violence in recent days appeared designed to further split the country along ethnic and religious lines, clerics from both Sunni and Shiite sects rejected the tactic in their Friday sermons.

Sheik Mahmud al-Sumadaei, an influential member of Sunni Scholars Association, said at western Baghdad's Um al-Qura Sunni mosque that Iraq denounced foreign fighters who "come across the border and kill us under the name of defending us."

Others condemned all sides, including the U.S. military.

"I hold the occupation forces, the Iraqi defense and interior ministers, responsible for the latest terrorist attacks that killed the innocents among our people," said Sheikh Mahdi al-Karbalaei said in the Shiite holy city of Karbala, 50 miles south of Baghdad.

For the Iraqi leadership, the challenge has been to ward off a seemingly endless insurgent campaign while winning the support of the country ahead of the referendum and Saddam's trial a few days later.

Some leading Sunni Arab groups have condemned the attacks against civilians. The government, trying to deflect an escalation of Sunni-Shiite sectarian tensions, has stressed that foreign fighters are behind much of the worst violence, pointing to the arrest of a Palestinian and a Libyan in Wednesday's Kazimiyah attacks on day laborers.

The bomber, they said, was Syrian. The government gave no evidence to support those claims.

Wednesday's massive bombings took place with both Iraqi President Jalal Talabani and Prime Minister Ibrahim al-Jaafari in the United States.

"Today, Iraq is facing one of the most brutal campaigns of terror at the hands of the forces of darkness," Talabani said Thursday, addressing the U.N. General Assembly with an appeal for international help.