"In case of an attack on a certain village, from the Janjawid, we used to ask them to mention the government forces with their Land Cruiser cars, in order to involve the government in the tribal clashes."
The group said they had decided to admit to their fabrications in an attempt to put an end to the crisis.
Al Jazeera's Mohamed Vall said the group claimed its false testimonies also helped build a criminal case against Omar al-Bashir, the Sudanese president, by the International Criminal Court (ICC).
The ICC issued a warrant for al-Bashir's arrest in March on counts of war crimes and crimes against humanity for his alleged role in the conflict in Darfur.
But the court ruled that there was insufficient evidence to prosecute the Sudanese leader for genocide.
Al-Bashir has denied the prosecution's allegations and has refused to recognise the court's jurisdiction.
He also expelled 13 international aid groups and three local aid organisations from Darfur after the ICC decision, accusing them of co-operating with the ICC against him, a charge the groups denied.
The government later agreed to allow some of the groups back in after international pressure.
The UN says the fighting in Darfur has killed up to 300,000 people and displaced an estimated 2.7 million.
But officials in Khartoum, the Sudanese capital, dispute the figures, saying that only 10,000 people have died since ethnic minority fighters rose up against the Arab-dominated government and its allies.
Government officials have hailed the activists' alleged confessions as vindication of their long-time denial of committing war crimes in Darfur.
"We will continue listening to these confessions with the UN, with the permanent and non-permanent members ... namely in terms of raising the awareness of the international community to the necessity to support the national efforts," Halim Abdul Mahmoud, Sudan's ambassador to the UN, said.
But Yahia Bolad, a spokesman for the rebel Sudan Liberation Movement, said the people making the allegations were not a part of Sudan's resistance group and were fabricating their claims.
"Many NGOs and many international leaders visited Darfur and they concluded that there are war crimes and crimes against humanity, and the United States also labelled it as a genocide," he told Al Jazeera.
"The evidence was there. The villages were destroyed, the IDPs [internally displaced persons], the refugees - this is clear evidence."