The attack occurred at the site of a and wounded 224 the day before. The toll was raised Thursday from a previous total of 18 killed.
The Thursday attacker was wearing an explosives vest under an Iraqi police uniform when he struck, killing Brig. Gen. Saleh Mohammed Hassan, the director of police for Ninevah province, of which Mosul is the capital, according to the statement.
The Iraqi army was securing the area, and a curfew was put in place across Mosul in the wake of the suicide attack.
An Iraqi police spokesman said Hassan was attacked after gunmen ambushed the blast site, sparking clashes that lasted for about 15 minutes. The bomber moved toward Hassan's car as it was preparing to flee the area, said Brig. Gen. Saeed al-Jubouri, a police spokesman.
Hassan was wounded and taken to an Iraqi army hospital, where he was pronounced dead, al-Jubouri said.
The ambush came first, as attackers opened fire on the police chief at about 9:30 a.m., as he walked through the wreckage with his entourage.
The brazen attack happened a day after a huge blast tore through a vacant apartment building and adjacent houses in the volatile northern Iraqi city just minutes after the Iraqi army arrived to investigate tips about a weapons cache.
American and Iraqi forces have been on the offensive against militants in and around Baghdad, but Mosul - Iraq's third-largest city some 225 miles northwest of the capital - continues to be a center of gravity for al Qaeda in Iraq and other insurgents, according to the U.S. military.
Duraid Kashmola, the governor of Ninevah province, of which Mosul is the capital, imposed an indefinite curfew in the city's downtown area following the clashes.
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.
A roadside bomb also struck a police patrol Thursday in central Baghdad, killing two officers and wounding two others, along with three civilians, police said. The explosion occurred about 8 a.m. in the predominantly Shiite neighborhood of Karradah.
The huge blast in Mosul went off Wednesday just after the troops arrived to investigate, and no soldier was reported killed.
Instead, the explosion ravaged dozens of old homes and collapsed a three-story building in a mostly Sunni neighborhood in Mosul, about 225 miles northwest of Baghdad.
Mosul, a major transportation hub with highways leading west to Syria and south to Baghdad, is considered a crucial conduit in the flow of money and foreign fighters to support the insurgency. The military said earlier this week that it was the last urban center with a strong presence of al Qaeda in Iraq.
Wednesday's explosion came shortly after the army received calls that insurgents were using the vacant building as a shelter and a bomb-making factory, according to al-Jubouri, the police spokesman.
Police raised the casualty toll on Thursday to at least 18 civilians killed and 146 injured as more victims were pulled from the rubble.