A series of car bombs have decimated Shiite-dominated neighbourhoods in cities across Iraq. The blasts occurred during Eid celebrations to mark the end of Ramadan.
At least 90 people have been killed and nearly 300 others injured.
The explosions are part of a recent surge in Iraq's Shiite-Sunni conflict, a bloody war which has claimed tens of thousands of lives over the past few years.
In total, 17 car explosions were reported across the strife-torn country, apart from series of shootings and other bombs.
The deadliest bombings took place in the Iraqi capital of Baghdad, killing more than 50 people. The coordinated attack targeted busy areas such as markets and cafes.
The US has called the attack a "cowardly" assault.
"The terrorists who committed these acts are enemies of Islam and a shared enemy of the United States, Iraq, and the international community. The attacks today bear the hallmarks of similar suicide and vehicle bomb attacks in Iraq over the past 90 days. Most of these attacks have been perpetrated by al-Qaida in Iraq," US State Department spokeswoman Jen Psaki said in a statement.
In July, more than 1,000 people were killed in escalating sectarian violence in Iraq. This is the highest death toll in a month since 2008, pushing the country yet again to the brink of all-out civil war.
During the Muslim fasting month of Ramadan, nearly 700 people are believed to have been killed.
No group has officially claimed responsibility for the attack.
The armed insurgency is mainly led by Sunni militants against the Shiite-led Baghdad administration. The conflict is also fuelled by intensifying bloodshed in neighbouring Syria.
The latest violence comes weeks after al-Qaida staged a massive jailbreak, freeing hundreds of inmates from the infamous Abu Ghraib prison.
Interpol has already warned the international community that the escape of al-Qaida-linked prisoners could lead to a further rise in violence.