Image copyright AFP Image caption News of the lawsuit comes just days after the second anniversary of the shooting.

The families of nine of the 26 people killed in a 2012 mass shooting at Sandy Hook Elementary School have filed a lawsuit against a rifle manufacturer.

The negligence and wrongful death suit was filed in Connecticut against Bushmaster Firearms International.

The families allege the Bushmaster AR-15 rifle used by Adam Lanza, 20, in the incident should not have been made publicly available because it was designed for military use.

Twenty children died in the attack.

"There is one tragically predictable civilian activity in which the AR-15 reigns supreme: mass shootings," the court documents state.

Image copyright Reuters Image caption Adam Lanza killed his mother at home before driving to the school

"Time and again, mentally unstable individuals and criminals have acquired the AR-15 with ease, and they have unleashed the rifle's lethal power into our streets."

On 14 December 2012, Lanza killed his mother, Nancy Lanza, before driving to the school and killing 20 children and six adults. He later took his own life when authorities arrived on the scene.

Other defendants in the lawsuit include firearm distributor Camfour and gun store Riverview Gun Sales where Nancy Lanza purchased the AR-15 rifle.

The plaintiffs in the lawsuit include Bill Sherlach, whose wife was killed in the shooting, as well as the families of victims Vicki Soto, Dylan Hockley, Noah Pozner, Lauren Rousseau, Benjamin Wheeler, Jesse Lewis, Daniel Barden, Rachel D'Avino and Natalie Hammond, who was injured in the attack.

"These companies assume no responsibility for marketing and selling a product to the general population who are not trained to use it nor even understand the power of it," Mr Sherlach told US media.

Defendants in the lawsuit have yet to comment publicly on the matter.