A roadside bombing killed at least six people and wounded 12 in the northern oil city of Kirkuk, a police source told Xinhua.
The attack targeted the convey of Colonel Jawdet Mohammed Abdulla, deputy chief of Kirkuk's police academy, said Brigadier-General Burhan Wasif of the Kirkuk police.
Abdulla survived the bombing with slight injuries, Wasif added.
Also on Wednesday, another explosion at a building in the northern city of Mosul killed at least 12 people and left more than 60 wounded, local police said.
The blast inside the residential building was a terror attack, Brigadier Abdul Krarim al-Jubury of the Mosul police told Xinhua.
He said that the blast took place at about 4:10 p.m. (1310 GMT)before the Iraqi security force and U.S. troops were about to enter the building on tips that explosives were inside.
The US military and the Iraqi troops are carrying out a large offensive mainly in northern Iraq to stamp out al-Qaida and other insurgents.
In two separate statements on Wednesday, the US military said that at least 20 terrorists have been killed in the day.
Security in Iraq dramatically improved over the past several months. The US military said that in December violence had dropped about 60 percent since last June, thanks to a large influx of U.S. troops and the cooperation of Iraq's Sunnis.
Yet, it warned that al-Qaida members, who had largely been squeezed out of Baghdad and the former hotbed of Anbar province, were regrouping in northern Iraqi provinces and still capable of launching remarkable attacks.
(Xinhua News Agency January 24, 2008)
