South Sudan provided logistical, financial and political support — but not weapons — to rebels fighting Sudanese government forces, according to a report from the Small Arms Survey, an independent Swiss research group.

South Sudan has often denied helping Sudanese rebels, but the research group says the government is providing vehicles, fuel and food to SPLM-North fighters and other rebel groups. There is also evidence that training may have been provided in a garrison in South Sudan's Western Bahr el Ghazal state. The SPLM-N operates on the Sudan side of the border between the two countries but is ideologically aligned with South Sudan.

Arnu Lodi, the SPLM-N spokesman, denied the report, saying the rebels have "not been receiving any support from the government of South Sudan."

Col. Philip Aguer, the spokesman for South Sudan's army, also denied the claims.

"It's not true. The northern rebels do not need South Sudan," Aguer said.

Jonah Leff, a researcher with the Small Arms Survey, said SPLM-North rebels and those belonging to a group called JEM, which operates mostly in Sudan's Darfur region, operate on both the northern and southern side of the border. The SPLA used to fight Sudan's military in a civil war and transitioned into South Sudan's own military force after the country became an independent nation in 2011, splitting off from Sudan.

The report titled "New War, Old Enemies: Conflict dynamics in South Kordofan," documents the first year of renewed fighting beginning in June 2011 between the SPLM-North rebels and the Sudan Armed Forces and paramilitary forces.

The SPLM-N rebels are made up of fighters who sided with South Sudan during its decades-long war for independence. They joined with other rebel groups in fighting that flared a month before South Sudan declared independence from Sudan. The fighting has extended across Sudan's South Kordofan and Blue Nile states. Sudan continues to bomb the region at periodic intervals.

The report says the rebels seized weapons, including machine guns, rockets and launchers and even tanks, from the Sudanese army between June 2011 and April 2012, reducing their dependence on outside sources.