A new report by a London-based research organization says Sudan has been supplying South Sudanese rebels with arms and ammunition.

The report by Conflict Armament Research, which investigates weapons trafficking, said 70 percent of the ammunition it has examined was recently manufactured in Sudan, which has been repeatedly accused by its southern neighbor of supporting rebels.

It added that most of the ammunition examined had sustained heavy impact damage consistent with witness accounts of aircraft dropping materials to the rebels between September and October last year.

Sudan routinely denies such accusations and a spokesman for the rebels, Dickson Gatluak, said the allegations were not true.

South Sudan broke away from Sudan in 2011 after decades of conflict, but relations remain tense with outstanding issues on borders and sharing oil revenues.