South Sudan moved a step closer to independence on Wednesday after organisers of its secession referendum said the vote's turnout would pass the 60 percent threshold it needed to be binding.

The announcement came as northern and southern leaders called two crisis meetings to resolve a surge of violence in border regions that has marred the plebiscite, in which southerners are widely expected to choose independence.

The final percentage (of participation) for the referendum process will exceed 60 percent, commission member Suad Ibrahim Eissa said in a statement.

Earlier on Wednesday, the fourth day of voting in the week- long poll, a senior southern official told journalists the turnout had already passed 60 percent.

We are aiming for 100 percent turnout by the end of the polling period, said Anne Itto from the south's ruling Sudan People's Liberation Movement (SPLM).

The referendum was promised in a 2005 accord that ended decades of civil war between the mostly Muslim north and the south, where most follow Christianity and traditional beliefs.

According to the regulations, the turnout needs to be 60 percent for the outcome to be valid. More than 50 percent of those voters need to choose independence for the south to secede. Preliminary results are expected in early February.

At least 46 deaths have been reported since Friday in clashes between northern Arab nomads and southern police, youths and refugees.

Some southern leaders have accused the north of arming the nomads to disrupt the referendum in a bid to keep control of the region's oil -- an accusation dismissed by Khartoum.

An underlying cause of the recent fighting has been the unresolved status of the fertile and oil-producing border area of Abyei, claimed by both Arab Misseriya nomads and the Dinka Ngok people, associated with the south.

Misseriya and Dinka leaders met on Wednesday in Kadugli, the capital of the surrounding state of Southern Kordofan.

We will see if they can reach an agreement ... Without hope you can't live, said Deng Arop Kuol, chief administrator of Abyei, a flashpoint of past north-south violence.

They will talk about the killings ... the cattle taken between the two sides, migration routes, issues of arms that are breeding conflict, said Kuol, a southerner.

On Sunday, a higher level meeting including Sudan's national and southern interior ministers and regional leaders would discuss the recent deployment of 300 southern police officers in Abyei, seen as a major cause of recent fighting, said Kuol.

A U.N. source said the Misseriya had suspected the new police were southern soldiers coming in to claim the region.

SPLM secretary general Pagan Amum said his party was ready to meet the north's ruling National Congress Party to discuss Abyei.

Abyei was one of the main battlegrounds in the north-south conflict which, fuelled by oil and ethnicity, was Africa's longest civil war and killed an estimated 2 million people.

The 2005 accord promised Abyei its own plebiscite on whether it wanted to join the north or the south. That vote was supposed to start on Sunday as well but it did not take place due to squabbling over who should be allowed to vote.

Kuol Deng Kuol, the paramount chief of the Dinka Ngok, earlier told Reuters he was going to the meeting in Kadugli.

The police deployed because of course there was a worry that there might be fighting, he told Reuters. I don't think they (the Misseriya) will stop (the attacks) because they are now preparing and approaching the area.

Commission spokesperson Eissa said 74 percent of southerners registered in the diaspora had voted and 36 percent in the north but had no separate figure for the south.

The underdeveloped south makes up a quarter of Sudan's land mass but has just 60 km (40 miles) of paved roads.

Sudan Sudan