At least 12 moviegoers were reportedly killed and 20 injured at a cinema in the Colorado city of Aurora in the Denver suburbs. They were attending a midnight showing of the new Batman film, The Dark Knight Rises.

The theater was packed with a lot of people, many of them young fans, at the time the shooting started, 9news reports. The violence erupted some 15 minutes after the movie started, witnesses said.

Some say that when they first heard the shooting, they thought it was some new type of special effect.

Local media reports that two gunmen were involved in the rampage. An explosive device was set off during the shooting, injuring several people.

Witnesses said the gunmen were probably wearing body armor and gas masks and used some kind of a tear gas bomb in the attack.

Some reports say police have apprehended one of the assailants while the second one is still at large.