The US military has launched a secret satellite from an Air Force base in California.

An Atlas V rocket lit up the night sky as it ascended from a launch pad at Vandenberg Air Force Base.

The rocket was carrying a "national security payload" for the US National Reconnaissance Office (NRO), an Air Force statement said.

The NRO oversees technical operations related to US spy satellites.

No details about the satellite's orbit or capabilities were released.

The take-off was the second of three launches the base has scheduled for September, the Air Force said.