Uganda's government has dismissed as "ridiculous" rebel leader Joseph Kony's claims that his Lord's Resistance Army was not involved in atrocities.
International rights group Human Rights Watch expressed surprise at Mr Kony's claim but said he must defend himself at the International Criminal Court.
Thousands have died in a conflict in which the LRA targetted children.
Mr Kony told the BBC the LRA was not responsible for killings, maimings and abductions in northern Uganda.
Ugandan government spokesman Robert Kabushenga said Mr Kony's denial was "ridiculous".
"A lot of information, a lot of evidence has been given by people abducted into the LRA," he told the BBC's Focus on Africa programme.
"Young children, people who were their commanders have all admitted publicly [to atrocities], and of course there are reports by journalists who have gone to areas where the LRA has been in and massacred."
HRW East Africa co-ordinator Jemera Rone said Mr Kony's insistence on his innocence was "amazing".
"We have testimony of extensive atrocities by the LRA," Ms Rone told the BBC News website.
She emphasised however that Mr Kony must be presumed innocent until proven guilty by the ICC, which has indicted him for war crimes.
"I think it is a good thing that Joseph Kony has come out of the woodwork and tried to engage with the international community, and I hope he will avail himself of the opportunity to clear his name," Ms Rone said.
Mr Kony described himself in an interview with the BBC's Newnight programme as a "freedom fighter" and called for peace talks.
He said stories of LRA rebels cutting off people's ears or lips were Ugandan government propaganda. He also denied his group kidnapped children.
"This is not true. I cannot cut the ear of my brother, I cannot kill the eye of my brother. I cannot kill my brother, that is not true," he said.
But earlier this year, UN humanitarian affairs chief Jan Egeland decribed the LRA's activities as "terrorism of the worst kind anywhere in the world" and the conflict as the world's worst humanitarian crisis.
Former BBC correspondent in Uganda, Will Ross, says Joseph Kony may describe himself as a freedom fighter but the LRA has had no clear political agenda and freedom is the last thing that he has brought as his rebels have caused widespread suffering and fear.
The rebels, claiming to be guided by the Bible's Ten Commandments, have caused insecurity in northern Uganda and southern Sudan.
The LRA has kidnapped many thousands of children over the years. It turns the boys into fighters or porters and uses many of the girls as sex slaves.
The south Sudanese vice-president, Riek Machar, is trying to broker a new peace initiative.
The Ugandan government says it is willing to discuss peace, but will not talk to those indicted by the international court.
HRW's Ms Rone said legal proceedings against Mr Kony "should not mean there are no peace negotiations in northern Uganda - the two should be independent of each other."
Ugandan President Yoweri Museveni has said that Mr Kony had until the end of July to end the war and said his safety would be guaranteed.