A security official said the bombing in Tikrit Monday destroyed several buildings in which the police, transportation and river rescue departments were housed, IraqiNews.com reported.
At least 20 people were injured, an official with Iraq's Interior Ministry said.
In Baghdad, also Monday, two policemen and a civilian were shot and killed by gunmen in two incidents, the ministry said. Two other people were wounded.
Officials said at least seven people were killed and more than 17 others injured in violence reported across the country Sunday.
Data compiled by government ministries for March indicated 163 Iraqi civilians, policemen and soldiers were killed and 256 others injured in acts of violence, CNN reported. The figures don't include the Kurdistan region in northern Iraq.