Bomb attacks killed 75 people in Iraq on Tuesday, including 48 who died in twin truck bombings in the northwestern town of Tal Afar, police said.
Among other attacks, suspected al Qaeda militants killed 21 people in bombings targeting police and Sunni Arab tribes who have formed an alliance against the militants, officials said.
The attacks follow an upsurge in violence in recent days. U.S. and Iraqi security forces have deployed thousands more soldiers in Baghdad to try to stem a sectarian war that threatens to tear the country apart.
Outgoing U.S. Ambassador Zalmay Khalilzad said on Monday al Qaeda was trying to undermine efforts by the Iraqi government to court tribal leaders and some insurgent groups to collaborate against the militant group.
One of the blasts in Tal Afar, a mixed town of Shi'ites, Sunni Arabs and Turkmen near the Syrian border, was detonated by a suicide bomber in front of a Shi'ite mosque, police and witnesses said.
Police Brigadier Karim Khalaf al-Jubouri said the bomber lured victims to buy wheat loaded on his truck. A second truck bomb exploded in a used car lot.
On Saturday, a man wearing an explosive vest blew himself up in Tal Afar, killing 10 people. In 2006, President George W. Bush held up Tal Afar as an example of progress being made in Iraq after U.S.-led forces freed it from al Qaeda militants in an offensive the previous year.
Near Ramadi, in western Anbar province, a suicide bomber exploded his car outside a restaurant on a main road, killing 17 people and wounding 32, a hospital source said.
The restaurant was frequented by police in an area where local tribes have joined the tribal alliance against al Qaeda. Many police were among the casualties, the hospital source said.
Earlier four people were killed in two blasts in Abu Ghraib, west of Baghdad. One of the dead was the son of tribal leader Sheikh Thahir al-Dari, said Ahmed al-Dulaimi, head of the provincial council media office in Anbar province.
Dulaimi said it was a double suicide car bombing, but a relative of the sheikh, a member of the anti-Qaeda alliance, said the son was killed when a rocket-propelled grenade hit the car he was in. Another person was wounded in the car.
Relatives blamed al Qaeda for the attack.
Dari's dead son, Harith al-Dari, is the nephew of his namesake who leads the Sunni Muslim Scholars' Association, an influential body of hardline clerics. The cleric has spoken out against the anti-Qaeda alliance that includes his own tribe.
Thahir al-Dari is the head of the al-Zobaie tribe, to which Deputy Prime Minister Salam al-Zobaie belongs. The deputy prime minister was the target of an assassination bid last week.
Suicide bombers have targeted a number of tribal leaders in the anti-Qaeda alliance amid a growing struggle in Anbar between the militant group and tribes who oppose its hardline form of Sunni Islam and indiscriminate killings.
Khalilzad, who left his post as ambassador to Iraq on Monday, said U.S. and Iraqi officials had held contacts with Sunni Arab insurgent-linked groups and were continuing to engage them to bring them into the political process.
In a move to address Sunni Arab concerns, Iraq's president and prime minister on Monday approved amendments to ease rules under which former members of Saddam Hussein's Baath party were banned from jobs in government and the security forces.
(Additional reporting by Ross Colvin and Mariam Karouny)