A renegade general who vowed to fight against the newly formed government in South Sudan is dead.

South Sudan Vice President Rick Machar confirmed the death of George Athor Deng Tuesday. Machar said he was killed Monday during a clash with government troops, saying Athor had been the most dangerous rebel leader in the country.

Athor, a former general in what is now South Sudan's army, rebelled against the government last year after losing a governor's race in Jonglei state, an election he claims was rigged. In the past year, his forces have carried out deadly attacks in Jonglei state and Upper Nile states.

Athor entered into peace talks with the South Sudanese President Salva Kiir's ruling Sudan People's Liberation Movement party last month. But those talks broke down and Athor said his forces were prepared to continue fighting against the government.

Athor and his South Sudanese Democratic Movement had been demanding new elections, the release of political prisoners, and the selection of a third party to help enforce any future peace agreement with the government.