Updated

Four days after Al Qaeda (search) in Iraq declared all-out war on the Shiite majority, more than 250 people have been killed, 30 of them by a car bomb Saturday outside a produce market in a poor Shiite suburb east of Baghdad (search). The blast underlined one of the bloodiest weeks since the U.S.-led invasion.

In all, at least 52 people were killed or found dead throughout the country Saturday, victims of mounting sectarian killings promised by Abu Musab al-Zarqawi (search), the Jordanian-born leader of the terrorist organization and a moving force behind the Sunni-dominated insurgency.

After a car bomber exploded his vehicle Wednesday in the midst of assembled day laborers in a largely Shiite neighborhood in north Baghdad, an audio tape posted on the Internet and claiming to be from al-Zarqawi announced "all-out war against Shiites everywhere. Beware, there will be no mercy."

The death toll from at least 14 bombings Wednesday was 167, marking the worst day of violence in the capital since U.S. troops invaded and overthrew Saddam Hussein (search) 21/2 years ago.

In Saturday's remote-controlled car bombing, Interior Ministry police Maj. Falah al-Mhamadawi said the vehicle was parked in front of fruit and vegetable stands in the market at Nahrawan, about 20 miles east of Baghdad.

Victims were taken to Baghdad's al-Kindi hospital in pickup trucks and minivans, police Lt. Abdulal Ibrahim said.

Some of the wounded — including those who lost limbs — lay bleeding on the hospital grounds.

"I came with my brother Hamid, whose right leg was blown off below the knee," said Alaa Mohammed, outside the hospital. "I saw neighbors putting him in a truck so I just jumped in with him."

Shiites have suffered the brunt of a massive campaign of bomb and shooting attacks, which al-Zarqawi said would continue against "any of (Iraq's) national guards, police or army (who are found to be) agents of the Crusaders (American forces). They will be killed and his house will demolished or burned — after evacuating all women and children."

But as the indiscriminate bombings continued into the weekend, the majority of the dead were Shiite civilians, prompting Islamic clerics from both the Sunni and Shiite sects to call for an end to the killing of innocent people.

"I call for a meeting ... of all the country's religious and political leaders to take a stand against the bloodshed," Sheik Mahmud al-Sumaidaei said during his Friday sermon at Baghdad's Um al Qura Sunni mosque.

"We don't need others to come across the border and kill us in the name of defending us," he declared, a reference to foreign fighters who have joined the insurgency under the banner of Al Qaeda. "We reject the killing of any Iraqi."

Throughout Iraq on Saturday, police reported finding 16 bodies that were blindfolded, bound hand and foot and shot. Two other people died in bomb attacks and four more were killed in shootings.

The bombing campaign, al-Zarqawi said, was launched in retaliation for a joint Iraqi-U.S. operation that chased his fighters and other insurgents out of their stronghold in the northern city of Tal Afar, near the Syrian border. Hundreds of insurgents reportedly were killed or captured.

The incessant attacks since Wednesday also have blunted the Iraqi military's ability to gain broader recognition for what, by all accounts, was a highly successful operation — the first in which Iraqi forces outnumbered Americans.

Earlier this week, the U.S. military spokesman in Baghdad said the spasm of violence was to have been expected after the operation in Tal Afar and before the Oct. 15 referendum on a new Iraqi constitution.

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

"Remember, democracy equals failure for the insurgency. So there has to be heightened awareness now as we work our way toward the referendum. That's power, that's movement toward democracy."

Also Saturday, a suicide car bomber attacked a U.S. convoy near Abu Ghraib prison west of Baghdad, destroying three vehicles, and insurgents shelled the notorious lockup with seven mortar rounds, said police Lt. Alaa Hussein.

In the same area, he reported, insurgents fired rocket-propelled grenades at a second U.S. convoy, damaging three armored vehicles.

The U.S. military issued no immediate casualty reports in any of the incidents.

Abu Ghraib was scene of the torture and execution of countless political prisoners under Saddam and of serious prisoner abuse by American forces after they toppled the dictator.

Also in western Baghdad, armed gunmen attacked a convoy of four trucks carrying food for the U.S. military. Two Sudanese drivers were killed, police and hospital sources said.

In the northern city of Mosul, coalition forces said they arrested two alleged leaders of Al Qaeda in Iraq.

The men — identified as Taha Ibrahim Yasin Becher (search), whose alias was Abu Fatima, and Hamed Saeed Ismael Mustafa (search), also known as Abu Shahed — allegedly headed the terrorist group's organization in Iraq's third-largest city.

A statement said they were arrested Sept. 5 and that Abu Fatima took over as Al Qaeda's top-ranking operative in Mosul after one of his predecessors was captured in June and another killed in August. He held the post for only 12 days, the statement said.