A barrage of car and suicide bomb blasts rocked Baghdad and two northern Iraqi towns yesterday, killing at least 61 people.
The bombers struck during a major holiday period to maximise the carnage.
The bulk of the attacks were in mainly Shi'ite Muslim parts of the Iraqi capital shortly after nightfall.
Authorities reported nine car bomb explosions across Baghdad, including one near a playground that killed two children.
Iraq is weathering its deadliest outburst of violence since 2008, raising fears the country is returning to the widespread sectarian killing that pushed it to the brink of civil war in the years after the 2003 US-led invasion.
Iraq's resurgent branch of al-Qai'da is believed to be behind the killing as part of its campaign to undermine the Shi'ite-led government.
Yesterday's bloodshed began when a suicide bomber blew up his bomb-laden car among houses in an ethnic minority village in northern Iraq. That attack, in the Shabak village of al-Mouafaqiyah near Mosul, killed at least 15 and wounded 52, police said.
The United Nations envoy to Iraq condemned the attack and said rising violence in Ninevah province required "urgent action and strengthened security cooperation" between regional authorities and the central government.
"The United Nations pays particular attention to the protection of minority communities who continue suffering from heinous attacks and economic and social barriers," envoy Nickolay Mladenov said.
Another suicide bomber struck hours later, setting off an explosives belt inside a cafe in Tuz Khormato, killing three and wounding 28, police chief Col. Hussein Ali Rasheed said.
The town, a frequent flashpoint for violence, sits in a band of territory contested by Arabs, Kurds and Turkomen about 200km north of Baghdad.
The attacks struck as Muslims around the world mark the religious holiday of Eid al-Adha, or the Feast of Sacrifice.
There was no immediate claim of responsibility for the blasts, though suicide bombings and car bombings are a favourite tactic of al-Qa'ida's local branch. It frequently targets Shi'ites, whom it considers heretics, and those seen as closely allied to the Shi'ite-led government in Baghdad.
Violence has escalated sharply since late April following a deadly crackdown by security forces on a camp for Sunni protesters in the northern town of Hawija.
The UN reported 979 people were killed violently in Iraq last month.
At least 350 more have died in attacks in Iraq so far this month, according to a count from a US news agency.