A homicide car bomber struck a predominantly Shiite neighborhood in central Baghdad on Thursday, killing at least 26 people and wounding 54, police said. The blast occurred shortly after two rockets slammed into the heavily fortified Green Zone.

Two hours later a second huge explosion rocked the area. Police said they had blown up a second car bomb that had been disabled before its second homicide bomber could detonate the vehicle.

A massive plume of black smoke rose into the air on the east bank of the Tigris River and heavy gunfire rang out across the city center in the aftermath.

The homicide bomber struck in the central neighborhood of Karradah, the second bombing to strike the area in three days. At least three policemen were among the dead.

Angry Shiite residents took to the streets chanting "We want the Sunnis out!" There is a small Christian and Sunni population in that section of the city.

Most of the bomb attacks in the sectarian warfare that has consumed the capital and central Iraq for the past year are believed to be the work of Sunni insurgents attacking Shiites.

The blast shattered windows in surrounding apartment buildings and devastated several vehicles as sirens from emergency vehicles wailed.

It struck shortly after the explosions in the Green Zone, which houses the U.S. and British embassies and Iraqi government offices, the public address system inside the massive compound could be heard warning in English that people should take cover, "this is not a drill."

The U.S. military said initial reports indicated that at least two rockets struck the Green Zone, but it said it could not give more details.

Karradah has been the site of several past bombings, including one on Tuesday that killed four people and wounded seven.

Ambulances raced from the scene, at least one with the back door still open and bodies stacked in the back, according to AP Television News footage. Smoke rose above the date palm trees lining the streets.

The explosion destroyed three minivans, 11 cars and dozens of shops as well as the neighborhood's post office, according to a resident.

The blasts came after Iraq's prime minister told parliament that the coming U.S-Iraqi security sweep in the capital would not be the last battle against militants, who he said would not be safe anywhere in the country.

Prime Minister Nouri al-Maliki did not reveal the details of the plan, which he has dubbed "Operation Imposing Law," or say when it would begin.

In his address to Parliament, al-Maliki promised to go after those behind Baghdad's rampant violence no matter where they tried to hide, although he promised to ensure the human rights of innocent Iraqis.

"We are full of hope. We have no other choice but to use force and any place where we receive fire will not be safe even if it is a school, a mosque, a political party office or home," he said. "There will be no safe place in Iraq for terrorists."

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His comments came a day after U.S. and Iraqi troops battled Sunni insurgents holed up in high-rise buildings on Haifa Street in the heart of Baghdad, with snipers on roofs taking aim at gunmen in open windows as Apache attack helicopters hovered overhead.

The Defense Ministry said 30 militants were killed and 27 captured Wednesday.

The military reported separately that an American soldier was killed Wednesday in clashes near the city's center, but officials declined to give more specifics or say whether the death was connected to the Haifa Street fighting. Two U.S. Marines also were reported killed Tuesday during combat in Anbar province, the military said.

Government spokesman Ali al-Dabbagh said the latest joint raid was aimed at clearing the area, which sits just north of the heavily fortified Green Zone, of "terrorists and outlaws" targeting residents. He promised such operations would continue as U.S. and Iraqi troops prepare for a broader security crackdown to stanch the sectarian bloodletting that has turned Baghdad into a battlefield.

But the operation drew condemnation from a Sunni group that said it was further proof that the Shiite-led government was targeting the minority sect.

The hard-line Association of Muslim Scholars condemned called the Haifa Street crackdown "a campaign of genocide" against Sunnis and said several buildings had been damaged and people killed. It said it had not determined the exact number of casualties because the area was under siege.

President Bush has committed 21,500 extra troops in a surge he hopes will succeed where other efforts have failed in quelling the sectarian violence.

Al-Maliki, a Shiite, also has placed high hopes on the operation and promised it will target Shiite militias and Sunni insurgents equally.

Past attempts by U.S. forces and Iraqis to secure the capital and many critics said it was because al-Maliki had intervened to prevent the crackdowns from going after members of the Shiite Mahdi Army militia that is run by one of his prime political backers, anti-American cleric Muqtada al-Sadr.

The militia force is believed responsible for much of the sectarian killing in Baghdad and central Iraq in recent months. Its forces and death squads have deeply infiltrated Iraqi security forces.

The crackdown "aims to disarm all groups and only leave weapons in the hands of the government," al-Maliki said, repeating a phrase he has used consistently. "This plan will not be the last. The battle between us and terrorists is open and continuous."

Meanwhile, the mayor of Baghdad's Sadr City said he reached agreement with political and religious groups to keep weapons off the streets of the heavily populated Shiite militia stronghold and has presented the deal to U.S. and Iraqi government officials in an apparent attempt to avoid a crackdown on the area.

Rahim al-Darraji said Iraqi troops will be in charge of security in the sprawling district in eastern Baghdad. His comments come amid fears that Sadr City, the main headquarters of the Mahdi Army militia, could be a major target in the planned crackdown.

Al-Maliki said five committees will be set up to work in conjunction with the military as it and U.S. troops conduct the security plan to deal with political, media, public services, economic and community outreach aspects.

He said Baghdad would be divided into nine sectors and Iraqi troops would be in the lead, backed by American forces.

The last of five additional U.S. brigades to help with the security sweep are scheduled to arrive in the Iraqi capital in May. The first, a brigade of the 82nd Airborne Division, arrived last week.

In violence Thursday, a bomb attached to a motorcycle exploded in one of Baghdad's busiest market areas, killing at least five people and wounding 20, police said.

The blast hit the Shorja market district about 11 a.m., police said, giving the casualty toll. The market is a major point for wholesalers to sell food, clothing and house products in the warehouses, stalls and shops lining the streets.

A bomb also struck a market in the religiously mixed area of Baiyaa in western Baghdad at 10:45 a.m., killing at least one civilian and wounding seven, police said.

Both areas have been the targets of bombings previously as insurgents seek busy commercial targets to maximize the casualties.

In northern Iraq, gunmen killed Hussein Abdul Aziz Ahmed, a member of the local council in Gayyara, about 20 miles south of Mosul, as he was driving to work, police said.

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