Brig. Gen. Salah Mohammed al-Jubouri, the police chief for surrounding Ninevah province, was killed as he left the blast site after being confronted by an angry crowd shouting "Allahu Akbar" or "God is Great" while he inspected damage near the crater.
Mosul, 225 miles northwest of Baghdad, has become one of the latest fronts in U.S.-led efforts to rid the country of al-Qaeda-linked militants who fled crackdowns in the capital and surrounding areas. While the levels of violence have fallen in much of the country, attacks have persisted north of Baghdad.
In Thursday's attack, a bomber disguised as a policeman blew himself up as the entourage was just yards away from their vehicles, said police spokesman Saeed al-Jubouri. Al-Jubouri is a tribal name common in Mosul.
The police chief was killed, along with two other officers, and five people were wounded, including three Iraqi police, an Iraqi soldier and a U.S. soldier, the U.S. military said.
The military said initial reports indicated al-Qaeda in Iraq was behind Thursday's attack, but Wednesday's explosion remained under investigation.
Ahmed Ibrahim, a 40-year-old tailor, said he went to the area early Thursday to check on his shop and found the building intact. But others were not so fortunate, finding entire blocks reduced to rubble and a massive crater at least 30 feet deep where the apartment building used to stand.
"The building that exploded has disappeared while the houses next to it were leveled. Other houses farther away were damaged," Ibrahim said.
"When I stood near the leveled houses, I heard the voices of people calling for help from under the debris. I went to the firefighters and told them about the voices," he said. "Some relatives were searching among the debris for their missing relatives. The whole thing is a disaster."
On Sunday, U.S. military spokesman Rear Adm. Gregory Smith said the military had largely chased al-Qaeda in Iraq out of all major urban centers except Mosul, the country's third largest city and a major transportation hub with highways leading west to Syria and south to Baghdad.
"Mosul will continue to be a center of influence for, a center of gravity for al-Qaeda because of its key network of facilitation - both financing and foreign fighters," he said. "The flow to Mosul is critical for al-Qaeda in Iraq."
Provincial Gov. Duraid Kashmola imposed an indefinite curfew starting at noon Thursday in the city following the attack.
He said a preliminary investigation showed al-Qaeda in Iraq was behind Wednesday's explosion in a bid "to terrorize Mosul residents."
Wednesday's explosion came after the Iraqi army received calls that insurgents were using the vacant building as a shelter and a bomb-making factory, police said.
A bulldozer worked through the night to clear the debris, with vehicles providing light as dozens of people watched on the rim of the water-filled crater, footage from the local TV station showed.
The TV footage showed one woman looking stunned as she held a bandage to her face in an emergency room and doctors rushed to treat a man whose face was bloodied.
The blast in Mosul was the latest in a series of bombings across Iraq, including in some areas that have seen a relative calm recently with the security gains from U.S.-Iraqi operations and a Sunni revolt against al-Qaeda in Iraq.
Al-Hamdani, the provincial council chief, said rescue operations continued despite the attack on the police chief and he expected the death toll to rise as more bodies were pulled from huge piles of concrete rubble.
Many of the recent attacks have been against Sunni tribal leaders and officials who have joined forces with the Americans against al-Qaeda in Iraq.
Clashes erupted for about two hours Thursday on the outskirts of Samarra, 60 miles north of Baghdad, between insurgents and members of the local Awakening Council, as the U.S.-allied group is known. A local police officer, who spoke on condition of anonymity because he feared retribution, said two militants were killed.
In other violence, a roadside bomb struck a police patrol in central Baghdad, killing two officers and injuring two, along with three civilians, police said. The explosion was in the predominantly Shiite neighborhood of Karradah.
An explosion also targeted a U.S. patrol in the mainly Shiite northeastern neighborhood of Ur but killed one civilian and wounded two others.