Sudan's government sold Sudanese- and Chinese-made weaponry to Qatar, which then arranged delivery to the Syrian opposition by way of Turkey, the rebels said.
The deals were not publicly acknowledged by Sudan, though, The New York Times reported Tuesday.
Such a deal could cause conflict with Sudan's close economic and diplomatic ties to Iran and China, both of which provide military and technical assistance to Sudan and might see such a sale of arms as fuel to the conflict and as a betrayal, the newspaper said.
Sudanese officials denied such a deal ever took place.
"Sudan has not sent weapons to Syria," said Imad Sid Ahmad, press secretary for President Omar Hassan al-Bashir.
Al-Sawarmi Khalid Saad, a spokesman for the Sudanese armed forces, said the allegations didn't make sense and could only exist as a smear against Sudan.
"We have no interest in supporting groups in Syria, especially if the outcome of the fighting is not clear," Saad said. "These allegations are meant to harm our relations with countries Sudan has good relations with."