The bomber detonated his explosives-laden car on Tuesday near police vehicles on the main road leading out of Kirkuk to Baghdad, police said.
Five of those killed were police officers, Colonel Burhan Tayyib Taha said. Many of the wounded were police, and the death toll is likely to rise as many of them were badly wounded, he said.
The US military surrounded the blast site.
The bombing follows a series of attacks across the country in the past five days in the build up to elections set for 15 December.
At least 160 people were killed in three days of violence starting last Friday, including 77 Iraqis killed in twin bomb attacks on Shia mosques in the mixed Kurdish and Shia city of Khanaqin.
“This is a phenomenon existing in the country. We are used to it”
Kirkuk, a mixed Arab, Kurdish and Turkmen city 250km (155 miles) north of Baghdad, has seen frequent episodes of violence, some caused by tensions between the communities, all of whom claim ownership of the city that is on oil reserves.
US troops were handing over some of Saddam Hussein’s former palaces to Iraqi forces on Tuesday in a ceremony attended by the American ambassador when two mortar rounds landed a few hundred metres away.
Witnesses said no one was hurt, but senior officials there, including the top US commander in Iraq, General George Casey, heard a loud reminder of the violence that has rocked the country since US-led troops toppled Saddam in 2003.
The ceremony was meant to symbolise how Iraqi troops are taking on more responsibility, but few local forces are able to fight armed opponents on their own, raising concerns that US forces might remain in Iraq for years.
American Ambassador Zalmay Khalilzad played down the blasts.
“This is a phenomenon existing in the country. We are used to it,” Khalilzad said after security guards rushed him to a safer place and then brought him back.
Two other US officials on another trip in Baquba were also exposed to the country’s instability.
A convoy transporting embassy staff and a high-ranking Iraqi election official was hit by a small makeshift bomb on a visit to Baquba, witnesses and officials said.
Iraq awaits general election
Izaddin al-Mohammedi, chairman of the board of directors of the Independent Electoral Commission of Iraq, was in the middle of the convoy with the embassy officials when the manually detonated bomb went off.
It was not clear whether al-Mohammedi or the convoy, which included several US military vehicles, was the target of the bomb, which hurt no one but slightly damaged one US military Humvee.
“Thank God we are alive,” al-Mohammedi said.
Al-Mohammedi, 43, continued to a meeting with local political leaders to explain the progress of planning for the 15 December election and to hear their grievances.
Iraqi fighters opposed to the US presence often use makeshift bombs, which are now the major killers of US soldiers in Iraq, accounting for almost 40% of deaths.
Three security guards were killed by armed men in al-Ghadir, 10km west of Karbala, a police source said.
In the western city of Ramadi, the capital of al-Anbar governorate, three policemen were shot dead by unknown assailants, and unknown attackers gunned down former intelligence officer Abd al-Wahab al-Dulaimi in his home in Ramadi, a police source said.
Also in al-Anbar, a US marine was killed in Habaniya on Monday when his vehicle was hit by a roadside bomb while on combat operations, the US military said in a statement.