NEW ORLEANS — An outbreak of violence has shocked New Orleans, with 17 people shot in an 18-hour period.

In all, 12 people have been murdered in the first 12 days of the year. At least two dozen, including a 12-year-old girl, have been wounded.

Mayor Mitch Landrieu calls it "a battle for the heart and soul of New Orleans."

It includes a gunman who opened fire inside a house Thursday, shooting five people. Three died. Police chased down a trio of suspects and returned fire, killing one and wounding two.

Later that night, police headquarters was evacuated when a pair of grenades was found in a car trunk. They were duds.

Police Superintendent Ronal Serpas says the shootings involving police may have been sparked by more aggressive tactics against known criminals.