Updated

The African Union envoy in charge of pursuing the Lord's Resistance Army claims that there are indications that its notorious leader Joseph Kony is seriously ill and on the run along the borders of Sudan's western Darfur region.

Francisco Madeira told reporters after briefing the U.N. Security Council on Wednesday that the nature of Kony's illness isn't known.

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 "a good number" of Kony's followers are defecting because of pressure from African troops supported by U.S. military advisers.

"From recent defectors, we know that some LRA leaders are reported to be seriously ill and requiring medicine." Ben Keesey, CEO of Invisible Children, told FoxNews.com. "There are rumors that Kony himself is one of the LRA needing medical treatment, but we have not seen evidence to substantiate this specific claim."

The LRA is notorious for kidnapping thousands of children to be soldiers and sex slaves.

The Associated Press contributed to this report.