A group of 19 soldiers in the Lord’s Resistance Army (LRA) has defected in the Central African Republic in the largest mass defection from the notorious rebel group since 2008, American advocacy group Invisible Children said Tuesday.

The California-based NGO heralded the defection in a press release as a huge victory for African Union-led efforts against the LRA, and said the defection was “non-violent.”

About 100 U.S. Special Forces experts are helping African troops to hunt down LRA fighters and their leader Joseph Kony, who is wanted by the International Criminal Court for war crimes and crimes against humanity.

Kony and his army are accused by the United Nations and human rights groups of killing and mutilating innocent civilians and kidnapping thousands of children and forcing them to be soldiers and sex slaves.

The African Union envoy in charge of pursuing the Lord's Resistance Army said last month many reports indicate Kony is seriously ill, and a “good number” of his followers are defecting.

 Francisco Madeira told reporters after briefing the U.N. Security Council Nov. 20 that the nature of Kony's illness isn't known but he is believed on the run along the borders of Sudan's western Darfur region and the Central African Republic.

He said Central African Republic President Michel Djotodia, a former rebel leader, told him that he and "his people" have been in contact with Kony, and "they want to encourage him to surrender."

Madeira said Kony's followers are defecting because of pressure from the U.S. and African forces.

The Associated Press contributed to this report