Speaking at the celebration, UN Secretary General Ban Ki-moon called for restraint as the US weighs intervention in Syria.
When South Sudan declared independence from Sudan, it took three quarters of the formerly united country's oil, which has since been a source of tension and conflict.
Sudanese government forces remain in the disputed Abyei region, flouting the first phase of the withdrawal schedule and complicating efforts to settle the area's status.
The thousands of Sudanese civilians who fled Abyei last month are wary about returning because they doubt the staying power of the most recent agreement to bring peace.
Chevron and the plaintiffs have both vowed to appeal the Ecuadorean court ruling, with the US oil company calling it 'illegitimate and unenforceable' and the plaintiffs saying the damages award is far too little.
Weeks before semiautonomous South Sudan votes on whether to secede from Sudan, people in the flashpoint border town of Abyei are concerned that a residency dispute could reignite a decades-long civil war.
While plans for South Sudan referendum move forward, preparations for a vote on Abyei, a contested border region that could join South Sudan, are making little headway.