A leading member of South Sudan's armed opposition says he was arrested and tortured in the capital before being released.

Dhieu Mathok, the secretary general of the SPLM-IO party and energy minister in South Sudan's new unity government, declined to name his attackers Thursday, saying only, "They are known."

A photo provided to The Associated Press showed Mathok's knees badly cut up, with chunks of skin missing.

"I am a leader of the IO and they want to assassinate me. That is all," he told the AP by phone.

Two other SPLM-IO officials separately confirmed the incident.

Opposing army factions have clashed in the capital, Juba, over the past week, with forces backing President Salva Kiir pushing many opposition forces out of their bases in the city.