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The radical cleric Muqtada al-Sadr issued a scathing attack on the United States on Friday, following one of the country's bloodiest days, blaming Washington for Iraq's troubles and calling for a mass demonstration April 9 — the fourth anniversary of the fall of Baghdad.

As al-Sadr's remarks were read in a mosque, Shiites in Baghdad loaded wooden coffins into vans and shoveled broken glass and other debris into wheelbarrows in the aftermath of a double suicide bombing at a marketplace. At least 181 people were killed or found dead Thursday as Sunni insurgents apparently stepped up their campaign of bombings to derail the seven-week-old security sweep in Baghdad.

Violence has increasingly erupted in towns and cities outside the capital in recent weeks, as insurgent fighters take their fight to regions where U.S. and Iraqi forces are thinly deployed. The U.S. military and its diplomats have voiced cautious optimism about the sweep that began Feb. 14 and emphasized that the full American surge force would not be in place until June.

An aide to Prime Minister Nouri al-Maliki pledged the government would persist in its efforts to stem the violence.

"There is a race between the government and the terrorists who are trying to make people reach the level of despair," the adviser Sami al-Askari said. "But the government is doing its best to defeat terrorists and it definitely will not be affected by these bombings."

Al-Sadr's statement was his first since March 14, when he urged his supporters to resist U.S. forces in Iraq through peaceful means. Al-Sadr has been said by U.S. and Iraqi officials to be in neighboring Iran, but his aides insist he is still in Iraq.

The latest statement was read to worshippers during Friday prayers at a mosque in Kufa, a Shiite holy city south of Baghdad where al-Sadr frequently led the ritual.

"I renew my call for the occupier (the United States) to leave our land," he said in the statement, a copy of which was obtained by The Associated Press. "The departure of the occupier will mean stability for Iraq, victory for Islam and peace and defeat for terrorism and infidels."

Al-Sadr, whose Mahdi Army militiamen fought U.S. troops in 2004 but have generally cooperated with an ongoing U.S.-Iraqi security push in Baghdad, blamed the presence of U.S. forces in Iraq for the rising violence, lack of services and sectarian bloodshed.

"You, oppressed people of Iraq, let the entire world hear your voice that you reject occupation, destruction and terrorism," he said in calling for the April 9 demonstration.

"Fly Iraqi flags atop homes, apartment buildings and government departments to show the sovereignty and independence of Iraq, and that you reject the presence of American flags and those of other nations occupying our beloved Iraq. Keep them there until they leave our land," he said.

Also on Friday, coalition forces detained a suspect who the U.S. military said was linked to networks bringing sophisticated roadside bombs into Iraq.

The suspect, who was detained during a raid in the Shiite militia stronghold of Sadr City, was believed to be tied to networks bringing the weapons known as explosively formed projectiles, or EFPs, into Iraq, the military said.

It did not identify the suspect or the groups he was accused of having ties to, but the U.S. military has asserted in recent months that Iran's Revolutionary Guards and Quds force have been providing Shiite militias with weapons and parts for sophisticated armor-piercing bombs. The EFPs are responsible for the deaths of more than 170 American and coalition soldiers since mid-2004, the military says.

The U.S. military also said a soldier was killed and another was wounded Thursday during a patrol in southern Baghdad, raising to at least 3,245 the number of U.S. service members who have died since the war began in 2003, according to an AP count.

Thursday's deadliest bombing was in Shaab, a predominantly Shiite neighborhood in northeastern Baghdad, where two suicide attackers wearing explosives blew themselves up in the Shalal market, which was crowded with shoppers seeking provisions on the eve of the Muslim day of rest and prayer. At least 82 people were killed and 102 were wounded, police and hospital officials said.

The Imam Ali hospital in nearby Sadr City was packed with the wounded on Friday, with two children lying in one bed, according to AP Television News video.

The Shaab neighborhood was one of the first that U.S. and Iraqi forces tackled when the security crackdown for which U.S. President George W. Bush has committed nearly 30,000 additional troops to dampen what had become uncontrollable violence in the capital. It also was the scene of a bombing nearly two weeks ago in which officials said a car bomber used children as decoys to get near the busy complex of shops and street vendors.

That attack occurred about two hours after three suicide car bombers struck a market in Khalis, a mainly Shiite town 80 kilometers (50 miles) north of the capital.

The drivers of the three suicide vehicle bombs, including an explosives-packed ambulance, detonated in a market that was especially crowded because government flour rations had just arrived for the first time in six months, TV stations reported. At least 43 people were killed and 86 wounded, police said.

The combined toll from the two bombings was at least 125 people killed and more than 150 wounded in one of Iraq's deadliest days in years.

The situation remained tense in Tal Afar, a religiously mixed Turkomen city that was the site of a devastating bombing on Tuesday followed by Shiite revenge attacks against Sunnis.

"Now the Sunnis are too afraid to cross Shiite areas and vice versa," said Mohammed Kamal, a 35-year-old Sunni teacher in the northwestern city. "Dead bodies are still being kept at the hospital because their relatives are too afraid to bury them in the cemetery because they would have to cross Shiite areas."

Provincial police chief Brig. Abdul-Karim al-Jibouri said 18 policemen suspected in the case were back in custody, a day after authorities said they had been released.

The U.S. military said it was providing meals, water, shelter and medical supplies to help residents who had been displaced by the bombing.

New U.S. Ambassador Ryan Crocker, meanwhile, presented his credentials to Iraqi Foreign Minister Hoshyar Zebari.

In the meeting, Zebari reiterated his stance that 15 British sailors and marines recently detained by Iran were "captured inside Iraqi territorial waters and were working in Iraq as part of the multinational force at the request of the Iraqi government."

Zebari, who called for the release of the British captives earlier this week, also said his government was in contact with Iran to "ensure the wise handling of the case."

At least eight people were killed or found dead In scattered violence Friday, including two civilians and an off-duty policeman who were shot to death in separate attacks in the northern city of Mosul.