A wave of bombings targeting Shiites in Iraq killed 72 people on Thursday, deepening sectarian tensions that exploded just after the last American troops left the country in mid-December.
The coordinated attacks targeting Shiites bore the hallmarks of Sunni insurgents linked to al-Qaida, although there was no immediate claim of responsibility.
The bombings began early in the morning when explosions struck two Shiite neighborhoods in Baghdad, killing at least 27 people.
A few hours later, a suicide attack hit Shiite pilgrims heading to the holy Shiite city of Karbala, killing 45, said provincial official Quosay al-Abadi. The explosions took place near Nasiriyah, about 200 miles southeast of Baghdad. Hospital officials confirmed the causalities.
The blasts occurred in the run-up to Arbaeen, a Shiite holy day which marks the end of 40 days of mourning that follow the anniversary of the death of Imam Hussein, a revered Shiite figure.
During this time, Shiite pilgrims from across Iraq make their way to Karbala, south of Baghdad.
Baghdad military spokesman Maj. Gen. Qassim al-Moussawi said the aim of the attacks is "to create turmoil among the Iraqi people." He said it was too early to say who was behind the bombings.
The new violence will only exacerbate the country's political crisis pitting politicians from the Shiite majority who dominate the government against the Sunni minority, which reigned supreme under the dictatorship of Saddam Hussein.
Shiite Prime Minister Nouri al-Maliki's government last month issued an arrest warrant for the Sunni vice-president, the country's top Sunni politician.
The Sunni official, Tariq al-Hashemi, is holed up in Iraq's semiautonomous Kurdish region in the north — effectively out of reach of state security forces.
The latest attack have only deepened the fears of a return to sectarian strife in Iraq, which teetered on the brink of civil war in 2006-7.
The attacks began in Baghdad with the explosion of a bomb attached to a motorcycle near a bus stop where day laborers gather to look for work in the Shiite Sadr City neighborhood. One of those who witnessed the attack said it filled the area with thick black smoke.
A Reuters reporter said there were blood stains all around the site of the motorcycle bomb attack and that tarmac on the road had been ripped up by the explosion. Building tools and shoes were scattered across the site.
"People have real fears that the cycle of violence might be revived in this country," said Tariq Annad, a 52-year-old government employee who lives nearby.
That attack was followed by the explosion of a roadside bomb. Police found a third bomb nearby and defused it.
The two Sadr City blasts killed 12 people, according to police and medical officials.
Less than two hours later, two explosions rocked the Shiite neighborhood of Kazimiyah in the north of the capital, killing 15 people.
Officials said the Kazimiyah blasts occurred almost simultaneously, with at least one caused by a car bomb. Simultaneous explosions are a tactic frequently used by the Sunni insurgents against Shiites.
Hospital officials confirmed the causalities from the four blasts, which included more than 60 wounded.
The officials spoke on condition of anonymity because they were not authorized to release the information.
Quosay al-Abadi, chief of Dhi Qar provincial council, said the Nasiriyah attacks targeted Shiite pilgrims
Photographs from the scene showed relatives hugging the bodies of young men lying face down on ground covered in blood and with the pilgrims' belongings strewn around them.
The last U.S. soldiers left Iraq on Dec. 18, ending a nearly nine-year war.