WASHINGTON (Reuters) - A new satellite image shows a marked increase in activity at a North Korean missile launch site, pointing to a possible long-range ballistic missile test by Pyongyang in the next three weeks, according to satellite operator DigitalGlobe Inc.

The imagery was released days after a Japanese newspaper, the Asahi Shimbun, reported that U.S. 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 U.S. 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 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 spokeswoman declined to comment on the reported satellite images, but said the Defense Department’s position on North Korea’s missile development efforts had not changed.

She urged North Korea to comply with U.N. Security Council resolutions that “require Pyongyang to suspend all activities related to its ballistic missile program in a complete, verifiable, and irreversible manner, and re-establish its moratorium on missile launching.”

North Korea, which carried out nuclear tests in 2006 and 2009 and is under heavy U.N. sanctions for its atomic 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 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 60 miles before crashing into the sea between South Korea and China.