The Sudanese government has airdropped weapons and ammunition to the SPLA-In Opposition rebels in South Sudan, a new report suggests.

A dispatch by Conflict Armament Research (CAR), which traces flows of weapons among armed groups, examined materiel captured by the SPLA from the SPLA-In Opposition in Pigi County, Jonglei state in November 2014. The dispatch, available for download below, concluded that the evidence suggests "direct supply from Sudan to SPLA-iO forces."

According to CAR Executive Director James Bevan, the evidence "clearly illustrates continuity in the types of weapon, and modes of delivery, employed by Sudan to sustain rebellion in South Sudan. Sudan's support for the SPLA-iO rebellion mirrors its assistance to South Sudanese rebel forces before the present crisis, and indeed before the latter country's independence."

The materiel that CAR examined included Sudanese-made Kalashnikov ammunition, Chinese-made bullets and rifles, and American-made rounds for recoilless rifles.

70 percent of the ammunition for Kalashnikov rifles was produced in Sudan, with much of it produced in 2014, after the South Sudan Civil War began. These bullets showed signs of damage from airdrops.

"Most of the ammunition documented suffered heavy impact damage, which is consistent with eyewitness reports that aircraft dropped materiel to SPLA-iO forces in September–October 2014," the report said. "Observers on the ground report that, throughout December 2014, aircraft dropped additional military equipment to SPLA-iO units in Upper Nile and Jonglei States."

Meanwhile, the Chinese-made rifles share serial number details with similar guns that Khartoum was previously documented supplying to rebel groups in South Sudan in 2011, before the current conflict. Other captured ammunition made in China was "identical" to ammunition supplied by Khartoum to South Sudanese rebels in 2012.

The weapons airdropped in Jonglei also mirror those found in other conflict zones known to be supplied by Khartoum, such as Darfur and the Central African Republic.

CAR also inspected three American-made recoilless rifle rounds recovered by the SPLA, including one captured in Malakal in March 2014 and brought to Juba. CAR said it sent an official trace request to the United States mission to the United Nations in New York for information on the history of those three rounds, but as of June 2015 did not receive a response.