Story highlights Report claims North Korea may be preparing for an ICBM launch

US President-elect previously said such a launch "wouldn't happen"

(CNN) North Korea may be reading two intercontinental ballistic missiles (ICBMs) for a test launch in the near future, according to US and South Korean officials.

US intelligence satellites have picked up signs of activity at North Korea's Chamjin missile factory southwest of Pyongyang, according to two officials familiar with the matter.

The US believes the activity could signal preparations for some type of ballistic missile test in the first days or weeks of the Trump administration, they said.

On Thursday, South Korea's Yonhap news agency quoted unnamed Korean military officials as saying two missiles have been placed on mobile launchers. The devices "are estimated to not exceed 15 meters (50 feet) in length, making them shorter than the North's existing ICBMs."

An official from Seoul's Joint Chiefs of Staff told reporters the claims could not be confirmed but said the military was monitoring the situation closely.