Iraqis inspect damage after a truck bomb exploded outside a Shiite mosque Tuesday, killing dozens and wounding more than 200 people.

Car bomb kills 78 in busy Baghdad square

BAGHDAD, Iraq (CNN) -- Atruck bomb ripped through a crowded square in the capital Tuesday, killing at least 78 people and wounding 224 others, an Interior Ministry official said.

The bomb erupted about 2 p.m. in Khalani Square, a busy commercial district near a Shiite mosque, the official said.

Prime Minister Nuri al-Maliki condemned the attack and blamed the blast on Saddamists and other extremists intent on stoking sectarian violence. (Watch authorities fight a fire at the smoking mosque)

Ten cars were destroyed in the blast, which sent a plume of smoke rising over rooftops in central Baghdad.

The Khalani Mosque also was damaged in the blast, authorities said. Video from the scene showed part of the wall surrounding the mosque collapsed.

The attack comes six days after insurgents blew up the two remaining minarets at the al-Askariya Mosque, a revered Shiite shrine in Samarra that was badly damaged in a February 2006 attack. (Watch how the Samarra tower was left in tatters after an attack blamed on al Qaeda)

Last week's blast sparked attacks on nine Sunni mosques in and around Baghdad the following day, but government and police officials expressed relief that the attacks paled in comparison to the wave of sectarian violence and reprisal killings that ensued after the 2006 attack.

The mosque damaged in Tuesday's attack houses the tomb of Mohammed al-Khalani, who was the second deputy and messenger of the Mehdi, the 12th imam from the early days of Islam who is revered by Shiites.

The Mehdi is said to have disappeared during the funeral of his father in the 9th century. Sunnis believe Allah withdrew the Mehdi from the eyes of the people and they are waiting for him to reappear as their leader.

The 10th and 11th Shiite imams are entombed at the Askariya Mosque.

22 killed in purported al Qaeda haven

Up to 10,000 U.S. soldiers backed by armored vehicles and helicopter gunships fought their way into an al Qaeda in Iraq haven in Baquba on Tuesday, killing at least 22 extremist fighters, the military said.

Operation Arrowhead Ripper, involving Strykers and Bradley Fighting Vehicles, was aimed at dismantling al Qaeda operations around Baquba, a hotbed of unrest north of Baghdad, a military statement said. (Watch a sniper v. sniper battle in Baquba)

Baquba is the capital of Diyala province, a mixed region located north and east of Baghdad and bordering Iran. Military officials believe some al Qaeda in Iraq elements have recently migrated from Baghdad and Anbar province to Diyala.

The 3rd Stryker Brigade Combat Team, 2nd Infantry Division kicked off the operation "with a quick-strike nighttime air assault earlier today," the military said Tuesday.

Ground troops joined the attack helicopters in engaging the militants, 22 of whom were killed by daylight, the military said.

The operation is in its opening stages, according to the military.

"The end state is to destroy the al Qaeda influences in this province and eliminate their threat against the people," said Brig. Gen. Mick Bednarek of the 25th Infantry Division. "That is the No. 1, bottom-line, up-front, in-your-face task and purpose."

Raids target insurgents across Iraq

Operation Arrowhead Ripper follows a series of raids over the past week by coalition troops that killed nine suspected terrorists, according to a statement. Twenty-two suspected terrorists were captured. The operations have been targeting al Qaeda in Iraq and other insurgents since Sunday. (Watch cockpit videos of air attacks in Iskandariya)

"Our continued pressure on the leaders and operatives of the al Qaeda network is denying them breathing space in Iraq," said Multi-National Force-Iraq spokesman Lt. Col. Christopher Garver. "The crumbling network has no place in the future of Iraq."

The raids were conducted in Anbar province, Dura'iya, Mosul, Baquba and the greater Baghdad area.

Further coalition raids aimed at disrupting the flow of weapons and fighters between Iraq and Iran left 20 militants dead early Monday in eastern Iraq, according to a statement.

Coalition aircraft strafed insurgent fighters who attacked troops in Amara and Majjar al-Kabir, two Shiite cities in the Maysan province bordering Iran, the military said.

"During the close air support, at least 20 terrorists were killed and six suspected terrorists were assessed to be wounded by the strafing," the military said. "A vehicle being used by the terrorists as a fighting position was also destroyed by the close air support."

Coalition forces captured militants who are "believed to be members of the secret cell terrorist network known for facilitating the transport of weapons and explosively formed penetrators, or EFPs, from Iran to Iraq, as well as bringing militants from Iraq to Iran for terrorist training," the military said.

The military said it has intelligence reports indicating that Amara and Majjar al-Kabir are smuggling routes for terrorists importing Iranian weapons into Iraq for the insurgency.

"Reports further indicate that Iranian surrogates, or Iraqis that are liaisons for Iranian intelligence operatives into Iraq, use both Amara and Majjar al-Kabir as safe haven locations," the military said.

The raids apparently involved Iraqi and British troops in a multinational force. British troops recently handed over security responsibility for the Maysan province to Iraqi security forces.

A British military spokesman said Iraqi Prime Minister Nuri al-Maliki personally authorized the raids.

Other developments

• Eight people died in fierce fighting that broke out Sunday between Iraqi security forces and the Mehdi Army, a Shiite militia, in southern Iraq, a Nasiriya hospital official said Tuesday. It was unclear Tuesday whether the clashes had ceased, but parliamentarian Bahaa al-Araji said the clashes ended when the two sides agreed to stop fighting.

• A U.S. soldier was killed Monday by small-arms fire while on patrol in eastern Baghdad, the military said Tuesday. The soldier was a member of Multi-National Division-Baghdad. Since the war started, 3,521 U.S. military personnel have died in Iraq. Seven civilian contractors also have been killed.

• Police found 33 bullet-riddled bodies across the capital Monday, the Interior Ministry reported. The total for June stands at 359, a ministry spokesman said Tuesday.

CNN's Mohammed Tawfeeq and Saad Abedine contributed to this report.