WASHINGTON - US President Barack Obama has promised every effort will be made to ensure the safety of Americans, a day after a shooting rampage in a Colorado movie theater killed 12 people.

"We are still gathering all the facts about what happened, but we do know the police have one suspect in custody. And the federal government stands ready to do everything necessary to bring whoever's responsible for this heinous crime to justice," Obama said in his weekly radio and Internet address Saturday.

US President Barack Obama during a moment of silence for the shootings in Colorado at an event in Fort Myers, Florida, July 20, 2012. [Photo/Agencies]

Police have detained James Eagan Holmes, 24, who allegedly killed 12 and wounded 59 at a midnight showing of the new Batman movie - The Dark Knight Rises, at Aurora, Colorado, a Denver suburb. The man surrendered without a fight in a parking lot behind the theater, police said.

The shooting reminded Americans of the Virginia Tech bloodbath in April 2007 in which 33 died. The FBI said there was so far no indication of any links to terror groups.

"We will take every step possible to ensure the safety of all our people. And we will stand by our neighbors in Colorado during this extraordinarily difficult time," Obama said.

Police said 30 victims remained hospitalized Saturday, 11 of them in critical condition.

"And if there's anything to take away from this tragedy, it's a reminder that life is fragile. Our time here is limited and it is precious," the US President said.

However, Obama didn't mention gun control, a sensitive issue for any candidate for the November presidential elections.

Gallup polls showed 39 percent of Americans owned a gun in 2010, while the National Rifle Association, a pro-gun lobby group, said almost half of US households possess guns.