( CNN ) -- South Sudan , the world 's newest nation , turned one year old on Monday , but its anniversary comes amid high tensions with its northern neighbor and economic concerns . With its capital in Juba , South Sudan became independent last year following decades of civil war . Its arrival in the international community was celebrated at the time , but conflict with the Sudanese regime soon resumed . Border clashes have brought the countries to the brink of war and left South Sudan coping with a massive humanitarian crisis as people flee the fighting . The South Sudan state of Upper Nile has been flooded with refugees crossing the border from Sudan . In total , aid agencies estimate that at least 150,000 refugees from Sudan are currently in South Sudan . The humanitarian problems have coincided with economic woes . The South Sudanese government lost 98 percent of its revenue when it halted oil production amid a dispute over transportation and processing fees with Sudan . South Sudan obtained around 70 % of the formerly united country 's oil reserves when it became independent last year . But the countries have been unable to agree on how much the landlocked South should pay to use infrastructure that remains in Sudan . South Sudan shut down production in late January after accusing Sudan of stealing $ 815 million worth of its oil . Sudan said it confiscated the crude to make up for unpaid fees . The shutdown has sent the economies of both countries reeling , but South Sudan has been hit particularly hard by the loss of income from virtually its only export . The young nation has also wrestled with corruption in its first year . In May , South Sudan 's president wrote to more than 75 government officials and eight foreign governments in an attempt to recover $ 4 billion lost through corruption .
South Sudan became independent last year following a two-decade civil war . Border clashes with its northern neighbor have put the region on edge . The fighting has created a huge humanitarian crisis . The South Sudanese government is also suffering from a lack of oil revenue .