At least 71 people died and 156 were wounded. Some of the bodies were badly charred, making identification difficult, reported the New York Times.
Several senior elected officials and civic and religious leaders spoke out against the violence on Sunday. Grand Ayatollah Ali al-Sistani asked the government "to defend this country against the mass annihilation," according to Vice President Adil Abdul-Mahdi, who led a delegation that visited the ayatollah on Sunday, the Times reported.
Saturday's attack was the most deadly in a wave of suicide blasts that has shaken Iraq over the past week, killing 170 people.
Insurgents had stolen a fuel tanker two days before Saturday's explosion, said an Oil Ministry spokesman. There were conflicting reports about the attack itself. Some witnesses said a fuel tanker was moving slowly in the center of the town when the blast occurred, but a tanker truck in the area was mostly intact, reported the AP.
On Sunday, four suicide car bombs killed 22 people, including an attack at the offices of Iraq's election commission that killed five election workers and one police officer.
The commission said in a statement that it "affirms its determination to continue the electoral process," including plans for a national referendum on a new constitution and balloting for a new government later in the year.
The violence continued Monday when insurgents killed six policemen and a government worker in six separate shootings across central Iraq.
Four of the police officers were shot in three of the attacks in southern and eastern Baghdad, police and hospital officials said.
One policeman was killed in a shootout between insurgents and security forces north of Baghdad in Taji, police said.
A police colonel was killed while driving his car in Samarra, 60 miles north of Baghdad, said police Capt. Laith Mohammed, reported the AP.
Also in the capital, insurgents killed a government worker for the Iraqi Trade Minister in the southern neighborhood of Dora.
Meanwhile, U.S. forces killed four insurgents preparing to launch mortars in the northern city of Tal Afar, the military said Monday.
Radical Shiite cleric Muqtada al-Sadr told BBC in an interview scheduled to air Monday that the continuing violence in Iraq was based in part on the presence of U.S. and other foreign forces in Iraq, reported the AP.
"The occupation in itself is a problem," he said. "Iraq not being independent is the problem. And the other problems stem from that -- from sectarianism to civil war, the entire American presence causes this."
U.S. Joint Chiefs of Staff Chairman Gen. Richard Myers said Monday the suicide bombings won't derail the country's progress toward democratization. A draft of a new constitution is expected this month ahead of a referendum on the document in October and elections in December.
"Every major milestone has been met. That will continue, in my belief, to happen," he said, according to the AP.