Violence in Iraq has been on the rise leading up to an Oct. 15 referendum vote on an Iraqi constitution.
Sunni insurgents have vowed to wreck the vote, declaring "all-out war" on the Shiite majority that dominates Iraq's government, reported the Associated Press. Moderate Sunni Arab leaders called on their community to vote against the charter, saying it will fragment Iraq and leave the Sunnis weak compared to Shiites and Kurds.
U.S. ambassador to Iraq Zalmay Khalilzad has been working with all sides to try to secure last-minute changes to the draft, which parliament approved Sept. 18 after weeks of difficult negotiations.
The car bombs exploded just before sunset in downtown Balad, 50 miles north of Baghdad, hitting a bank, a vegetable market and another location, Police Lt. Ghafil Hassan said, according to the AP.
At least 60 people were killed, and among the 70 wounded were the police chief and four officers, said Dr. Khaled al-Azawi of Balad Hospital.
A major U.S. air base is located on Balad's outskirts.
In Ramadi, 80 miles west of Baghdad, a roadside bomb exploded during combat Wednesday, killing five Americans, a Marine statement said. The blast brings to 1,934 the number of U.S. service members who have died since Iraq's war started in March 2003, according to an AP count.
More than 140 people -- including 13 U.S. service members -- have been killed in the past four days.
In Washington, the top American commander in Iraq testified before Congress Thursday that the process of withdrawing U.S. troops depends on the results of the referendum and elections set to take place if the constitution passes.
"The next 75 days are going to be critical," Gen. George Casey told the Senate Armed Services Committee.