The Sudanese military has deployed military hardware near the flashpoint Abyei border region, monitoring group Satellite Sentinel Project has said.
About two Mi-24 helicopter gunships, nine T-55 tanks and heavily armoured trucks were deployed about 60 miles from oil-enriched Abyei's border.
The build-up of firepower near the disputed region could trigger renewed conflict between the north and south Sudan militaries.
Satellite Sentinel Project director of operations Nathaniel Raymond said the move represented an additional threat to the human security of civilians in and around Abyei.
The Abyei region is claimed by both north and south Sudan and both militaries have been building up resources around the central region.
Southern Sudan voted for separation from the north in January, and is designated to become the world's newest country in July this year.