Insurgents in Iraq have carried out a series of attacks Tuesday north of Baghdad against the country's security forces, killing at least 23 police and national guards.

Eighteen policemen were among the dead. Authorities say a combination of gunmen and car bombs were responsible for the violence in and near the towns of Tikrit, Samarra, Balad and Baquba.

In Baghdad, officials say a senior National Guard officer survived an apparent assassination attempt when a car bomb exploded near his home. At least six guardsmen were wounded in the blast.

U.S. Brigadier General Jeffrey Hammond told reporters in Baghdad that the U.S. military in Iraq expects an escalation in attacks and assassination attempts ahead of the January 30 elections.

Some information for this report provided by AP, AFP and Reuters.