A gunman opened fire at a movie theater in Colorado early Friday, killing 12 people and injuring 38 others, authorities said.

The shooting occurred in the Denver suburb of Aurora at the 16-theater Century complex, which was packed with hundreds of people, including many children, for the midnight opening of the Batman movie "The Dark Knight Rises."

Aurora Police Chief Dan Oates told local television that officers apprehended a 24-year-old suspect shortly after the shooting spree in a parking lot behind the cinema complex.

The man, who had a shotgun, a rifle, a pistol and a bullet-proof vest in his possession, told the officers he had explosives at his apartment.

Cellphones images captured scenes of panic and people injured at the movie complex in Aurora, 15 kilometers (nine miles) northeast of Denver, where the shooting occurred at around 12:30 a.m.

Local authorities said the injured were taken to three Aurora hospitals for medical care.

Police described the rifle used in the attack as an automatic weapon.

FBI special agent Jim Yacone said that agency had dispatched personnel to cooperate in the investigation, adding that dozens of people were being interviewed at a local high school.

One witness said she saw a 9-year-old girl with bullet wounds in the back, while 30-year-old Benjamin Fernandez told the Denver Post that he was watching the movie when he heard a series of explosions, adding that people ran out of the theater while police were shouting "get down!"

Salina Jordan, 19, who was in another theater, told the same daily that she saw several people injured, including a girl who had been shot in the cheek and others with bullet wounds in the stomach.

Oates had earlier said 14 people were killed - 10 at the movie complex and four others at local hospitals - but that figure was later revised downward.

The Batman film has numerous high-volume sound effects and a witness told CNN that the movie-going public did not initially notice that the shots in the front of the complex came from real firearms.

President Barack Obama, on a campaign trip in Florida, described the killings as "horrific and tragic." EFE