Three car bombs exploded in the capital Baghdad, killing an Iraqi civilian and wounding 18, an interior ministry source said.
Two of the bombs appeared to target passing police cars.
An army lieutenant-colonel was shot dead in southern Baghdad, while three municipal employees, including an Egyptian, were gunned down while working in the west of the capital.
Two of their colleagues were wounded.
Also in Baghdad, gunmen shot dead the Iraqi driver of a Jordanian embassy car at a petrol station, according to Jordanian government spokesman Nasser Jawdeh.
Outside of the capital two Shiite tribal leaders and a municipal head were shot dead in Khan Abi Saad, 30 kilometres north of Baghdad.
While 10 people were wounded as a roadside bomb and a booby-trapped motorbike blew up in nearby Baquba.
In the northern city of Kirkuk, police said, an army captain and a soldier, acting as his bodyguard, were shot and killed.
Insurgents change targets
"We're seeing the insurgent move his target away from coalition forces to Iraqi security forces," US Major-General Rick Lynch said.
He attributed the spike to the increased role of Iraqi security forces, as well as the interim period between the December 15 elections and the formation of a new government, which is still pending.
"We have seen over the last several weeks about a 15 percent increase in civilian casualties, and we've seen about a 30 percent increase in attacks against security forces," he told reporters.
"The insurgents want to attack because they want to discredit the government in existence, so seeing spikes in attacks during this period in time was not indeed unpredicted." Major General Lynch added.