Armed men wearing army uniforms seized Ammar al-Saffar, Iraq's deputy health minister, from his home in Baghdad's Sunni district of Adhamiyah.
One interior ministry source said the co-ordinated attack on the Mashtel bus garage, near the New Baghdad district, involved three car bombs.
Another source in the ministry and one at police headquarters said the nature of the third device was unclear.
Sunday's suicide bombing in Kirkuk took place shortly after sunset as people gathered to pay condolences to the family of a Kurdish man who was shot dead late on Saturday, said Brigadier-General Sarhad Qader.
Sunni fighters swept through parts of the city of Baquba, northeast of Baghdad, attacking a police checkpoint and shooting residents after dragging them from their homes and cars, police said on Sunday.
Police had imposed a day-long curfew in Baquba, which is thought to be one of Iraq's most dangerous cities, after Saturday's attacks in the city.
Eleven bodies with bullet wounds were brought to the city morgue, hospital and police sources said.
A senior policeman, who asked to remain anonymous, told Reuters: "There is not a day that passes without dozens of people being killed either from bombs, shootings or assassinations. This has been going on for months."
The figures could not be verified. Reuters typically reports several violent deaths a day in the province, but much of the region is inaccessible to both the media and security forces.
By Sunday morning, police had lifted the curfew but had blocked off the main street in the city. Gunmen remained in control of four districts and attacked a second checkpoint, police said.