The imagery was released days after a Japanese newspaper, the Asahi Shimbun, reported that US intelligence analysts had detected moves that were seen as preparation by North Korea for a long-range missile launch as early as this month.
DigitalGlobe, which provides commercial satellite imagery to the US government and foreign governments, on Monday released a new image that it said showed increased activity at North Korea's Sohae (West Sea) Satellite Launch Station.
It said the imagery showed more people, trucks and other equipment at the site, a level of activity that was consistent with launch preparations seen before North Korea's failed April 13 rocket launch.
"Given the observed level of activity noted of a new tent, trucks, people and numerous portable fuel/oxidizer tanks, should North Korea desire, it could possibly conduct its fifth satellite launch event during the next three weeks," DigitalGlobe said in a statement accompanying the image.
A Pentagon spokesman had no immediate comment.
North Korea, under heavy UN sanctions for its nuclear weapons program, has tried for years to influence major events in South Korea by waging propaganda or armed attacks. South Korea is gearing up for a presidential election on December 19.
North and South Korea have been technically at war since their 1950-53 conflict ended in a truce, not a peace treaty, and regional powers have for years been trying to rein in the North's nuclear program.
North Korea is believed to be developing a long-range ballistic missile with a range of up to 6,700 km (4,200 miles) aimed at hitting the continental United States but the last two rocket test launches failed.
In April, under its new leader Kim Jong-un, North Korea launched a rocket that flew just a few minutes covering a little over 100 km (60 miles) before crashing into the sea between South Korea and China.