Clashes struck Sudan's north-south border Saturday, including in the nation's disputed flashpoint area of Abyei, sobering up an otherwise jubilant atmosphere in southern Sudan on the eve of the region's historic vote for independence.
The violence, instigated by pockets of small militias, seems to be contained for now. Polling for the referendum is set to open on Sunday as planned.
For most of the past 50 years, Sudan's southern region has been at war with Sudan's government in the north. The weeklong popular plebiscite beginning Sunday in southern Sudan offers the oil-rich region the choice to secede and form a new nation. The vote was a core component of the 2005 US-brokered deal that ended the latest civil war.
World leaders have expressed concern that the expected vote for separation could inflame old tensions between the two sides and possibly lead to renewed conflict, especially along the two sides' long shared border, where many areas remain disputed.
In Abyei, northern-aligned Arab Misseriya nomads have clashed twice with armed Ngok Dinka, the district's ethnic southern permanent residents who want the area to join the south, according to the region's Ngok Dinka administration.
The United Nations, which has a peacekeeping base in the district, wasn't able to confirm casualties on Saturday.
Abyei is widely thought to be the most explosive flashpoint along the border. In 2008, some 100 people were killed and tens of thousands displaced after fighting between the northern and southern militaries broke out in breach of the ceasefire.
"We call upon the leaders to ensure that the people of Abyei, the constituents, can have their needs, their aspirations, and their rights met," Scott Gration, U.S. Special Envoy to Sudan, told reporters Saturday in Juba, the southern capital.
For the past two days, fighting has also erupted between southern forces and militiamen loyal to Gatluak Gai, a southern rebel leader, in Southern Sudan's border state of Unity. Six have been killed, according to the Southern Sudanese army.
Distrust remains high between the two war-time enemies. "This attack is clearly designed to disrupt the referendum process," said Southern Sudan army spokesman Philip Aguer, who blamed northern elements for supporting Gai's forces.
The violence Friday and Saturday stood in stark contrast to the outpouring of joy and optimism from Juba in recent days, where pro-secession public rallies and widespread excitement have built upon the buzz of anticipation ahead of the vote.
Tuesday, during a rare visit to Juba, Sudanese President Omar al-Bashir vowed to respect a southern decision for secession.
"We are left only with a few hours to make the most vital and extremely important decision of our life time," Southern Sudan's leader, Salva Kiir, said in a public address Saturday.
The southern referendum is an "extraordinary moment," Kerry said in Juba Saturday. "It's something I think the whole world should take pride in."