BAGHDAD — Car bomb blasts and other explosions tore through mainly Shiite districts around Baghdad during morning rush hour Wednesday in a day of violence that killed at least 80, intensifying worries about Iraq's ability to tame the spiraling mayhem gripping the country.

It was the latest set of large-scale sectarian attacks to hit Iraq, even as the government went on "high alert" in case a possible Western strike in neighboring Syria increases Iraq's turmoil.

A relentless wave of killing has left thousands dead since April in the country's worst spate of bloodshed since 2008. The surge in violence raises fears that Iraq is hurtling back toward the widespread sectarian killing that peaked in 2006 and 2007, when the country was teetering on the edge of civil war.

Most of Wednesday's attacks happened in within minutes of each other as people headed to work or were out shopping early in the day. Insurgents unleashed explosives-laden cars, suicide bombers and other bombs that targeted parking lots, outdoor markets and restaurants in predominantly Shiite areas in and around Baghdad, officials said. A military convoy was hit south of the capital.

Security forces sealed off the blast scenes as ambulances raced to pick up the wounded. The twisted wreckage of cars littered the pavement while cleaners and shop owners brushed away debris. At one restaurant, the floor was stained with blood and dishes were scattered on plastic tables.

"What sin have those innocent people committed?" asked Ahmed Jassim, who witnessed one of the explosions in Baghdad's Hurriyah neighborhood. "We hold the government responsible."

The northern neighborhood of Kazimiyah, home to a prominent Shiite shrine, was among the worst hit. Two bombs went off in a parking lot, followed by a suicide car bomber who struck onlookers who had gathered at the scene. Police said the attack killed 10 people and wounded 27.

There was no immediate claim of responsibility for the attacks, but they bore the hallmarks of the Iraqi branch of al-Qaida, which operates in Iraq under the name the Islamic State of Iraq and the Levant. The group frequently targets Shiites, which it considers heretics, and carries out coordinated bombings in an attempt to incite sectarian strife.

Charles Lister, an analyst at IHS Jane's Terrorism and Insurgency Center, said the group is increasingly showing "huge confidence and military capability."

"Both the increasing frequency, and statistically, the increasing deadliness of (their) coordinated nationwide bombings in Iraq underlines the extent of their operational reach and the huge depth of their resources," he said.

In one particularly brutal attack, a Shiite family was shot dead at home in the largely Sunni town of Latifiyah, about 30 kilometers (20 miles) south of Baghdad. Four children, ages eight to 16, were killed along with their parents and an uncle, police said. Authorities said they had previously fled the town after being threatened and had returned only three weeks ago.

Many of the day's blasts targeted morning shoppers. One parked car bomb in a commercial area in Baghdad's northern Shaab killed nine. Parked car bombs that went off in outdoor markets killed 19 in the sprawling slum of Sadr City, the northeastern neighborhood of Shula, the southeastern Jisr Diyala district and the eastern New Baghdad area.

Blasts also hit the neighborhoods of Bayaa, Jamila, Hurriyah and Saydiyah, killing 12. Yet another car bomb exploded in the evening in Baghdad's southwestern Amil neighborhood, killing four.

Outside the capital, a suicide bomber blew himself up near a restaurant in Mahmoudiyah, about 30 kilometers (20 miles) south of Baghdad, killing five. And in Madain, about 25 kilometers (15 miles) southeast of Baghdad, a roadside bomb struck a passing military patrol, killing four soldiers.

While Shiite areas bore the brunt of the attacks, Sunni areas were targeted late in the day.

A parked car bomb exploded late Wednesday as worshippers left a mosque in Baghdad's western Yarmouk neighborhood, killing four. Several Sunni mosques have been attacked in recent months, raising the possibility that largely inactive Shiite militias are starting to carry out retaliatory attacks.

Later, police said a parked car bomb hit a coffee shop in the largely Sunni neighborhood of Azamiyah, killing six.

Medical officials confirmed the casualty figures, which included more than 250 wounded. All officials spoke on condition of anonymity as they were not authorized to release information.

The deputy United Nations envoy to Iraq, Jacqueline Badcock, condemned the blasts and urged authorities to do more to protect the Iraqi people.

The violence follows months of protests by Iraq's Sunni minority against the Shiite-led government that began late last year. Attacks have been rising since a deadly crackdown by security forces on a Sunni protest in April. In response, clerics and other influential Shiite and Sunni leaders have called for restraint.

More than 510 people have been killed so far in August, according to an Associated Press count.

The sectarian tensions fueling Iraq's spiraling violence are being exacerbated by the civil war in Syria, where largely Sunni rebels are fighting to topple President Bashar Assad, who is backed by regional Shiite powerhouse Iran.

Iraq's government, which has bolstered ties with Iran in the years since the 2003 U.S.-led invasion, has an officially neutral stance on the Syrian civil war. It has long called for a negotiated political settlement to the conflict.

Al-Maliki, the Iraqi prime minister, said Wednesday that Iraqi security forces and other government institutions are on high alert to protect against any domestic consequences of a possible Western-led military action in Syria.

The prime minister did not elaborate, but Iraqi officials fear that Sunni extremists fighting in Syria could bring their fight to Baghdad if Assad is toppled. Further unrest in Syria also could send more refugees into Iraq. More than 44,000 have flooded into the north of the country just since Aug. 15.

"We have taken every necessary action to protect our country from any dangerous developments that may result from the Syrian crisis and from the possible strike," al-Maliki said in the televised address.