JUBA // The dispute began innocently with a football landing outside the pitch at Juba University.
But when a passing student kicked it into the distance and the players rushed to beat him, a full-blown tribal conflict erupted on the campus. A hundred students squared off the next morning, threatening each other with sticks and stones.
Several were injured, including one whose leg was broken. Administrators closed the university. It has not been reopened since the March 27 clash.
The confrontation highlights simmering tribal tensions in South Sudan, the world's newest country.
Whether the nation can calm those rivalries will affect whether South Sudan will survive as a democracy or collapse into a stillborn state. With fighting raging along the border with the Republic of Sudan and the country's economy in sharp decline, some observers fear South Sudan's government is in danger of fracturing.
South Sudan has more than 60 tribes, with the Dinka as the single largest group, spread out among 10 states on more than 620,000 square kilometres of land. The most violent tribal clashes have taken place in rural communities over territory and cattle. But the trouble at Juba University shows that these disputes have come to the capital, where many say the Dinka use their strength to give jobs and positions of power to fellow tribesmen.
"People still think about their tribes first, their nation second," said Ajang Ajang, 29, president of the Juba University student union, who tried to mediate between the two groups before fighting broke out.
The battle, he said, was a direct consequence of his decision to ban tribal associations on campus in February. Association members unsuccessfully tried to force him from his position, leaving a tense atmosphere at Juba University before the football fight.
He said he banned tribal associations because "we are all South Sudanese. We respect tribal culture, but we need to follow national laws and be unified."
During the secession from Sudan last year, South Sudan appeared to be entering a new era in a land that had seen ethnic conflict for decades. Two million people died during the civil war between the north and south and another four million were driven from their homes. The 21-year war ended in 2005 with the signing of a peace agreement by the Sudanese Peoples' Liberation Army in the south and the Sudan Armed Forces in the north.
South Sudan approved secession in January 2011, with 98 per cent choosing independence from the Arab- and Muslim-dominated north. South Sudanese are predominantly Christian or follow indigenous religions.
But efforts to disarm militias that were once part of the independence movement and reconcile feuding tribes have failed. Earlier this year, 125,000 people were displaced in the state of Jonglei, located to the north-east of the capital of Juba, after a new round of attacks by members of the Lou Nuer tribe on residents of Pibor county, home to the Murle tribe, according to the United Nations.
An estimated 1,000 tribesmen were killed, women and children abducted and cattle stolen. Some survivors bear the scars from machete wounds. The two tribes have presence throughout East Africa; the members in South Sudan live mostly in Jonglei.
The government disarmament mission has seen violence, too. Khawam Bol Dut, 26, a soldier, was brought to Juba Military Hospital from Jonglei with wounds indicating he had been tortured, according to the admitting doctor. His arms were so swollen from being strung up to a tree that his right arm had to be amputated below the elbow. Lying underneath a mosquito net with a seeping chest wound and a bandaged stump where his arm used to be, he could not coherently recount what had happened to him.
Tribal conflicts are having repercussions throughout South Sudan. The border war with the north is complicated by attacks by militias that both sides supposedly are supporting. But this is a simplistic assumption: the largely tribal-based militias have their own agendas, even if they receive some kind of support from governments. Once they receive weapons, it will prove difficult to get them back.
Many Juba University students had been unable to finish their studies while the university was closed throughout the civil war. Some were able to relocate to campuses in Khartoum. Now, with classes cancelled for more than a month, seniors expecting to graduate may have to wait another year. That, in turn, affects job prospects and family livelihoods.
Even if they had graduated, their job prospects would heavily depend on their tribal affiliations, said Salah Khalil, an analyst from Cairo's Al Ahram Centre for Strategic and Political Studies.
"The tribes, especially the Dinka, are very strong inside the government," Mr Khalil said. "The law of the country is still the law of the tribes. If your ethnic group falls out of power, you lose everything."
Members of the Dinka hold the main positions in the government, he said.
That was part of the problem at Juba University, said Mr Ajang, who is a member of the Dinka.
"Even when I tried to get rid of the tribal associations, they thought I was trying to make the Dinka stronger," he said. "The leaders of the associations feared they would be left out."