Updated

A series of explosions ripped through Baghdad on Saturday to bring the death toll around Iraq to at least 23 people, a day after a suspected shoe bomber blew himself up inside one of Baghdad's most prominent Shiite mosques, killing 13 people.

A total of seven blasts occurred within a span of five hours and dealt a new blow to a massive security operation launched earlier this week by the Iraqi government to secure the capital.

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, Capt. Rashid al-Samarie said. 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 20 miles south of Baghdad, killing one civilian and wounding three others, all from the same family, al-Samarie said.

A soldier in the U.S.-led coalition also was killed Friday and two others were missing after an attack on a checkpoint near the town of Youssifiyah, 12 miles south of Baghdad, the U.S. military said.

The first attack in the capital occurred about 9:50 a.m. when a mortar shell was fired at one of Baghdad's oldest markets in the predominantly Shiite suburb of Kazimiyah, killing at least four people and wounding 13, police Capt. Mohammed al-Waili 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 civilians and wounding 24, some seriously, police Lt. Ahmed Mohamed Ali said.

A roadside bomb also missed a police patrol about 10:40 a.m. in Karradah, a popular shopping area in downtown Baghdad, killing one civilian and wounding two, police Col. Abbas Mohammed said.

About 20 minutes later, a suicide car bomb targeting an Iraqi army patrol near the Wathiq Square in the same neighborhood, killing seven people, including 4 soldiers and wounding 10 people, including two civilians, police Lt. Ali Mitab said.

In the New Baghdad area of eastern Baghdad, a bomb left in a plastic bag left aboard a mini bus exploded, killing three passengers and wounding 15 others, police Maj. Maher Mousa said.

A car bomb in western Baghdad wounded 6 people, while a roadside bomb struck an Iraqi police patrol in downtown Baghdad, wounding two officers.

The surge in violence has shattered a fragile calm imposed by the security crackdown launched Wednesday in the capital.

On Friday, a suspected shoe bomber targeting a Shiite imam who criticized Abu Musab 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.

The mosque's imam, a leading Shiite politician, blamed Al Qaeda in Iraq for the attack. He said the terror group was trying to reassert itself after the death of its leader in a U.S. airstrike last week.

"Al Qaeda is trying to restore some respect after the killing of the terror leader Abu Musab al-Zarqawi by targeting one of the leading Shiite clerics, but they will fail," said the imam, Jalal Eddin al-Sagheer.

The imam, who was not injured, said the bombing came after guards found two pair of explosive-laden shoes outside the mosque. The guards entered the mosque and began searching everyone who had carried their shoes inside, he said.

When they approached the attacker, he detonated what would have been a third pair of explosive-laden shoes, he said.

"The guards discovered two pair of shoes full of explosives. That got them to start searching all the worshippers. When one of them tried to search the suicide bomber, he blew himself up," al-Sagheer said.

But the Interior Ministry, noting the scale of destruction, suggested the attacker may have detonated a vest rather than shoes. Police Lt. Thaer Mahmoud said the attacker was indeed wearing a suicide vest.

The device contained metal balls and fragments, according to an Interior Ministry police officer who could not be named because he was not authorized to speak to reporters. Metal balls and fragments could fit into either shoes or a vest.

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 Zarqawi.

Al-Sagheer said the terror group had threatened to kill him in an Internet posting this week. A similar warning preceded the April attack, he said.

He said Al Qaeda accused him in the latest posting of being behind deaths squads targeting Palestinians living in Baghdad. Since the Saddam Hussein era, a large contingent of Palestinians, who are Sunni Arabs, has lived in Baghdad.

On Friday, Al-Jazeera aired an audio tape of a key insurgency leader calling 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 Qaeda in Iraq. The authenticity of the tape could not immediately be verified.

Significantly, the speaker does not mention the man identified by the U.S. as Al Qaeda in Iraq's choice to replace Zarqawi — Abu Ayub al-Masri, also known as Abu Hamza al-Muhajer. The lack of such a reference may suggest that al-Baghdadi does not support him.

There has been a slight decrease in the number of Iraqis reported killed since al-Zarqawi died June 7. In the nine days before the airstrike, 307 Iraqis were killed compared with 262 in the nine subsequent days, according to an Associated Press tally.

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, 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.