Sudan opposition leader Yasir Arman arrived in Juba, South Sudan on Monday after he was released together with two other rebel leaders by the military junta.
Mr. Arman is the deputy chairperson of the Sudan People's Liberation Movement/ Army- North (SPLM/A/N), an armed faction based in the Blue Nile region.
He had been arrested on June 5 by the Sudan's Transitional Military Council (TMC) for allegedly fuelling protests in the crisis-hit country.
He had earlier defied a military ultimatum that he leaves the country on accusations that he was positioning himself to become the President of Sudan with the help of foreign financiers.
The rebel leader was accused of enjoying foreign backing and positioning himself to become the President of the Sudan.
The release of the trio - the others are Ismail Jalab and Mubarak Ardol - is believed to have been negotiated by Ethiopian premier Ahmed Abiy who was on a reconciliation mission in Khartoum last week.
Mr Abiy met TMC, Alliance for Freedom and Change and other political leaders with a message that Sudan reverts to democratic rule.
Jalab and Ardol were detained from their residences after meeting with Mr Abiy Ahmed in Khartoum on Friday for talks aimed at reviving negotiations between the generals and protest leaders.
Arman arrived in Khartoum on May 26 to take part in talks with Sudan's ruling generals who took power after the ouster of president Omar al-Bashir in April following months of mass protests against his authoritarian rule and worsening economic conditions.
On June 3 military forces raided a sit-in outside the army headquarters in Khartoum, starting a week of violent crackdown that has officially left 61 dead, 49 of them from live ammunition.
The protesters put the toll at 118.
The SPLM-N's armed wing has battled Bashir's forces in the Blue Nile and South Kordofan states since 2011.
The rebel group is part of the Alliance for Freedom and Change. It had set Arman's release as one of several conditions before any fresh negotiations with the generals could begin.
The protest movement wants the ruling military council to hand over power to a civilian-led administration.
The protesters started a nationwide civil disobedience campaign on Sunday, paralysing transport and shutting down cities like Omdurman, al-Obeid and Port Sudan.
In the capital Khartoum, however, several shops and fuel stations opened and buses ran on Monday, the second day of disobedience.
The health ministry says 61 people died nationwide in last week's crackdown, 49 of them from "live ammunition" in Khartoum.
Additional reporting by agencies