(CNN) -- The former U.S. ambassador to Iraq, Ryan Crocker, blames al Qaeda for Tuesday's coordinated bomb attacks in Iraq, saying al Qaeda is now targeting the Iraqi government.
The bombings -- the latest in a series of attacks in Iraq -- killed eight people.
Calling al Qaeda in Iraq a "very deadly adversary," Crocker said in an interview with CNN's Christiane Amanpour that al Qaeda was working "to shake popular confidence in the (Iraqi) government, particularly as we move toward elections."
In Tuesday's attacks, insurgents exploded three car bombs close to heavily guarded sites in the Baghdad city center near the fortified "Green Zone" that houses Iraqi government buildings and the U.S. embassy. Four people were killed and 14 others were injured. In the volatile northern city of Mosul, four people were killed in three bombings.
"It's pretty clear to me that the architect is al Qaeda in Iraq," Crocker told Amanpour.
The bombings in Baghdad came a week after a string of attacks that killed nearly 130 people in the Iraqi capital and wounded 400 others. They were the worst in the city since October when car bombs killed and wounded hundreds. Overall though, the number of Iraqi civilians killed in the war has fallen to the lowest levels since the U.S.-led invasion in 2003.
Crocker -- who is now dean of the George Bush School of Government at Texas A&M University -- said al Qaeda in Iraq is shifting its tactics. He said al Qaeda previously launched bombings targeting the civilian population in an effort to restart sectarian violence, but it didn't work.
"Iraqis simply refused to be provoked into that kind of widespread carnage that we saw in '06 and '07," he said. "So al Qaeda shifted to take on the (Iraqi) state, and I don't think that's going to work either."
Crocker said the upcoming Iraqi elections, scheduled for early March, are going to be very important for the country's development. But he warned there will be new security challenges, echoing concerns expressed by the U.S. commander in Iraq, Gen. Raymond Odierno.
The United States has stopped patrolling Iraqi urban areas, under an agreement with the Baghdad government that was implemented in June. The U.S. will withdraw all its combat troops from Iraq by the end of August next year, leaving a residual force of up to 50,000 troops. There are about 115,000 American forces in Iraq now, while Iraq has nearly 700,000 troops and police in its security forces.
The U.S. Special Inspector General for Iraq Reconstruction, Stuart Bowen, said the United States has spent a huge sum of money on building up Iraq's army and police.
"Eighteen billion dollars in the Iraq security forces fund and another $7 billion in other resources into the Iraqi army and police have built a pretty credible force that should be able to keep the peace across the country, notwithstanding these notable attacks," Bowen told Amanpour.
Bowen also highlighted what he described as the enormous economic success that Iraq realized over the weekend, when it awarded seven new contracts to develop its oil fields. Those oil fields have the potential to double Iraq's oil production to 5 million barrels a day within a few years.
"There is an economic engine waiting to be unleashed. It's in the ground in Iraq. That oil has to be gotten out and exported," Bowen said. "If the Iraqis can do that while fighting corruption and keeping this insurgency down, then prosperity lies ahead."
But a leading Iraqi advocate for women and children's rights, Basma Al-Khateeb, had a less rosy outlook for Iraq. She said security in Iraq remained "quite fragile."
Asked whether she is worried about the withdrawal of American forces from Iraq, she said, "The occupation and the American forces' role is not really one of the issues that are making trouble here. We have more complex and complicated issues that we need to solve."
Al-Khateeb said the chaos in Iraq has made many Iraqis lose faith in democracy. But she added that Iraqis themselves will eventually solve their problems, even if the elections do not lead to any change, pointing to the possibility of a new era in politics in the future.
"We want elections to pass through, but also we expect more political powers and movements to rise from the new generation in Iraq," she said.