Updated

Insurgents killed more than three dozen people in a series of attacks that foiled stringent security measures around Baghdad after an Al Qaeda threat to stage bloody reprisals for the death of Abu Musab al-Zarqawi.

U.S. troops combed through the so-called "Triangle of Death," a predominantly Sunni Arab region just south of Baghdad for two soldiers that went missing after an attack that killed one of their comrades at a traffic checkpoint.

U.S. Maj. Gen. William Caldwell said four raids had been carried out since Friday's attack and that ground forces, helicopters and airplanes were taking part in the search.

Countrywatch: Iraq

The soldiers came under attack at a traffic checkpoint next to a canal southwest of Youssifiyah, 20 kilometers (12 miles) south of the capital. The area is considered and insurgent hotbed.

"We are currently using every means at our disposal on the ground, in the air and in the water to find them," Caldwell said.

The Baghdad attacks dealt an embarrassing new blow to Premier Nouri al-Maliki's pledge to bring peace to the capital — which has been flush with new police and army checkpoints following a plan announced last week to restore security for Baghdad's more than five million residents.

His Sunni Arab deputy prime minister, Salam Zikam Ali al-Zubaie, charged that the plan was not properly thought out and needed more work.

"I can say that I am not pleased with the way the Baghdad security plan began," he told al-Jaazera TV. "The Baghdad plan has begun, but it will need a year or more to finish."

Al-Zubaie said for it to succeed, the interior ministry responsible for carrying it out had to be cleansed of people who may be responsible for "human rights violations." Many Sunni Arabs charge the Shiite-dominated security services have been infiltrated by militias.

"There are a lot of responsible people who were responsible for committing numerous acts of foolishness and many human right violations who are still in positions of responsibility," he said.

A total of eight blasts killed at least 27 people in Baghdad and injured dozens. At least 11 other people died around Iraq.

The violence included a suicide car bomber who exploded his vehicle as it was being towed near a police checkpoint in Mahmoudiya, south of Baghdad, killing four civilians and wounding 15. The bomber had claimed his car had broken down and hired a tractor to tow it while he rode inside, al-Samarie said.

A mortar barrage also hit a residential area in Mahmoudiya, a predominantly Sunni city about 30 kilometers (20 miles) south of Baghdad, killing one civilian and wounding three others.

In the Baghdad attacks, a mortar shell was fired at one of Baghdad's best known markets, which dates back more than 100 years, in the predominantly Shiite suburb of Kazimiyah, killing at least four people and wounding 13, police said.

Nearly half an hour later, a bomb left in a plastic bag struck an outdoor market where secondhand goods are sold in central Baghdad, killing two people and wounding 24, some seriously. Police added that a suicide bomber targeting an Iraqi army patrol near Wathiq Square in the same neighborhood killed seven people when he blew himself up.

A parked car bomb in southwest Baghdad killed six people and wounded 36, police said.

Three mortar rounds hit an open-air popular market in the al-Bour area of northern Baghdad, killing two and wounding 14. The rest died in other a number of other roadside bombings around the capital.

The surge in violence has shattered a fragile calm imposed by a security crackdown launched a week after al-Zarqawi's death.

On Friday, a suspected shoe bomber targeting a Shiite imam who criticized al-Zarqawi blew himself up inside the Buratha mosque during the main weekly religious service, killing 13 people and wounding 28. That attack was carried out despite a four-hour driving ban intended to prevent suicide car bombs during Friday prayers.

It was the second attack on the Buratha mosque in just over two months. On April 7, four suicide bombers, including a woman, set off their explosives during Friday prayers, killing at least 85 worshippers. The U.S. military blamed al-Zarqawi.

On Friday, Al-Jazeera aired an audio tape of a key insurgency leader calling al-Zarqawi's death a "great loss" but saying it will strengthen the militants' determination.

The broadcaster identified the voice as that of Abu Abdullah Rashid al-Baghdadi, the head of the Mujahedeen Shura Council, which groups five Iraqi insurgent organizations including al-Qaida in Iraq. The authenticity of the tape could not immediately be verified.

In other violence Saturday, according to police:

— Gunmen attacked the house of Iraqi army Col. Makki Mindil, killing him after engaging his guards in a gunfight. Four guards also were wounded in the 8:20 a.m. attack in Amarah, 290 kilometers (180 miles) southeast of Baghdad. The bullet-riddled body of another Iraqi soldier was found elsewhere in the city.

— Police also found two bodies, handcuffed and shot in the head, in separate areas of eastern Baghdad.

— Gunmen in speeding car shot and killed a student in the College of Nursing in northern Mosul as he was walking near his dormitory, police said.

— Gunmen killed two Baghdad University students in a drive-by shooting that took place western Baghdad. Another man was killed in a similar shooting in the al-Shurta district, police said.

— Three people, including a police officer and city councilman, were killed in Diwaniyah, 130 kilometers (80 miles) south of Baghdad.

— The body of a man who had been tortured and had his eyes gouged out before being shot was found in southwestern Baghdad, police said.