A key broker of the latest deal to end South Sudan's civil war diverted European weapons to South Sudan's military despite an EU arms embargo, a new report says. It also asks how a US military jet ended up deployed in South Sudan in possible violation of arms export controls.The London-based Conflict Armament Research report , released on Thursday, raises questions about Uganda's support for neighbouring South Sudan's government even as it promotes itself as a neutral negotiator in one of Africa's deadliest conflicts.South Sudan's warring sides signed the peace agreement in September to end a five-year civil war that has killed nearly 400 000 people. Previous deals have collapsed in gunfire. The new report is a "forensic picture of how prohibitions on arms transfers to the warring parties have failed," said Conflict Armament Research's executive director, James Bevan.The report says Uganda bought arms and ammunition from at least three EU members - Bulgaria, Romania and Slovakia - that were diverted to South Sudan's military and armed allies in Sudan. The transfers occurred before the United Nations Security Council imposed its own arms embargo on South Sudan earlier this year but well after the EU embargo.With the Bulgarian weapons, "South Sudan arranged for Uganda to issue end-user certificates (the essential paperwork for an international arms transfer) ... to make it look like these weapons were for the use of the Ugandan armed forces when in fact they were always destined for South Sudan," said Mike Lewis, the head of regional operations for Conflict Armament Research.It is less clear whether Uganda's government, a key US security ally in the region, was complicit in the diversion of ammunition shipped to it from Romania and Slovakia in 2015, Lewis said. Some of the ammunition was discovered with Sudan-based militias allied with South Sudan's military.Uganda's government did not reply to evidence sent to it, Lewis said. Uganda's military spokesperson, Brigadier Richard Karemire, told The Associated Press he had not seen the report. "For us, we support the peace process in South Sudan," he said.South Sudan's information minister Michael Makuei Lueth rejected the findings as fake. "We don't even have money to buy arms and now we need money for the peace agreement," he told the AP. He added: "How can they pass an arms embargo and expect others to abide by it? If the EU has passed an arms embargo that's up to them, but we in African countries, we're not a member of the EU and we're not bound by it."As for the exporting countries, there is no suggestion they were complicit in, or even aware of, the diversion, the new report says.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook. Uganda in the past has openly provided support to South Sudan's government during the civil war, which erupted in late 2013 between supporters of President Salva Kiir and then-deputy Riek Machar. The latest peace deal once again returns Machar as Kiir's deputy; a previous attempt at that arrangement failed amid fresh fighting in July 2016. The new deal, largely brokered by Uganda and Sudan, faces skepticism from the United States and others.Sudan in the past quietly supplied Chinese-made ammunition to South Sudan's armed opposition, the new report adds. Chinese ammunition has made up 99% of the ammunition that Conflict Armament Research has documented in South Sudan since 2014.The report also describes how a network of "jointly owned Ugandan and US companies - controlled by British, Israeli, Ugandan, and US nationals - procured a military jet from the United States and an Austrian-made surveillance aircraft, which one of these companies delivered into service with (South Sudan's military) in 2015 and 2016, respectively."Based on interviews and commercial documents, the report found that the company, Yamasec, transferred both aircraft to South Sudan's military. The US military jet, after being used by Uganda's air force, was deployed in South Sudan in 2016, overflying armed opposition targets along with attack helicopters.The military jet's previous private owner in the US told Conflict Armament Research that "Yamasec USA LLC took responsibility for obtaining a US Department of Commerce dual-use export license," the report says. "The Department of Commerce, however, has stated that it issued no such license" and it is not clear whether the State Department issued a required military export license.The Uganda-based Yamasec Ltd used the plane to train members of Uganda's air force, the report says. While the transfer to Uganda was not illegal, "re-export to South Sudan may have violated non-retransfer conditions under US arms export controls."Yamasec did not reply to Conflict Armament Research, nor to the AP.