Pyongyang could carry out a long-range missile test, Seoul has warned, as new satellite images showed increased activity at its launch site.

Satellite imagery provider DigitalGlobe released an image Monday showing a “marked increase in activity” at a launch site near the Chinese border, AFP reports.

“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 even during the next three weeks,” DigitalGlobe said.

Early this month, a US think tank predicted a missile launch with satellite images indicating activity.

The launch could pose a threat to stability on the Korean peninsula ahead of the South Korean presidential elections in December, Seoul said.

“It’s clear that they’re in preparation for a possible launch,” a senior foreign ministry official told the Financial Times.

Seoul is concerned that the North would use the provocation to gain leverage and influence the polls as both candidates pledged to improve relations with the rogue state.

North Korea has criticized the South Korean government, accusing election-frontrunner Park Geun-Hye and President Lee Myung-bak’s New Frontier party of being “wicked confrontation maniacs” and having “wrecked peace and stability on the Korean peninsula”.

Pyongyang has threatened direct assaults on South Korea after activists floated propaganda balloons and warned it would repeat the 2010 shelling of Yeonpyeong island as border tensions run high.