Image caption James Holmes is alleged to have planned the attack

Three people injured in the Colorado theatre massacre in July are suing the cinema owners over inadequate security.

Cinemark USA "failed to provide for the safety and security of its theatre and its patrons," the lawsuit says.

Measures "would likely have prevented or deterred the gunman from accomplishing his planned assault on the theatre's patrons", it says.

James Holmes is accused of killing 12 and wounding 58 at the premiere of the new Batman film in Aurora.

The 24-year-old was a graduate student at the University of Colorado, Denver, but was in the process of dropping out after failing a key exam.

Attorney Christina Habas who filed the lawsuit on behalf of Joshua Nowlan, Denise Traynom and Brandon Axelrod said in a press release: "The lawsuit is based upon Cinemark's failure to provide for the safety and security of its theatre and its patrons.

"Although the theatre was showing a midnight premiere of the movie and was expecting large crowds of people to attend the midnight showing, no security personnel were present for that showing," the lawsuit says.

Prosecutors say that Mr Holmes bought a ticket to the film before leaving through an exit door and propping it open to return later to open fire, armed with several weapons.

Cinemark has not commented.