Hundreds of Rapid Support Forces were mobilised on Sunday in parts of North Darfur near the border with Chad, local sources said.
The deployments came amid an exchange of drone strikes, raising fears that fighting could expand toward the strategic border town of Al-Tinah.
Sources said reinforcements gathered in Ad Al-Khair, Jarjirah, Qadir and Al-Adwa as tensions rose across remote desert communities.
Across the border, a source in Chad said the Chadian army reinforced its presence and began digging trenches along parts of the frontier.
Despite tighter controls at border crossings, Sudanese civilians continue fleeing into Chad.
A volunteer in North Darfur said displacement toward Chad has increased sharply in recent days, with more than 1,000 displaced people relying on emergency kitchens amid severe shortages of food and drinking water.
