* International observers give thumbs up to south Sudan poll
* "Virtually certain" of vote for separation - Carter Center
(Adds U.S. reaction paragraphs 7-8)
By Andrew Heavens
KHARTOUM, Jan 17 (Reuters) - International observers gave south Sudan's independence referendum their seal of approval on Monday and said a vote for secession was now "virtually certain" in their first official judgment on the poll.
Early results from last week's plebiscite suggest people from Sudan's oil-producing south voted overwhelmingly to split away from the north after decades of civil war.
Observers from the Carter Center and the European Union both said the vote had been credible, an endorsement that moved the region a step closer to independence.
"The European Union election observation mission assess the voting process of the Southern Sudan Referendum credible and well-organised in a mostly peaceful environment," a preliminary statement seen by Reuters said. <^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ For a take a look on Sudan click on [ID:nLDE70708L] For a Q+A on south Sudan independence click on [ID:nMCD452310] Key political risks to watch in Sudan click on [ID:nRISKSD] ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^> Former U.S. President Jimmy Carter's mission said a number of irregularities had not undermined the legitimacy of the referendum, which hopes to end a violent cycle of bitter north-south conflict in Africa's largest country.
"The (Carter) Center finds that the referendum process to date is broadly consistent with international standards for democratic elections and represents the genuine expression of the will of the electorate," its statement read.
U.S. Secretary of State Hillary Clinton praised both southern and northern leaders for creating conditions in which voters could cast their ballots "freely and without fear."
"The parties have an opportunity to forge a durable peace between the North and the South," she said in a statement, adding that the United States supported their efforts "to ensure a peaceful, more prosperous future for all Sudanese."
In the southern capital Juba, six centres each had more than 2,500 votes for secession compared with a maximum of just 25 votes for unity.
Around 97 percent of southerners voting in Egypt chose separation, compared with just 2 percent for unity, the poll's organising commission said on Monday.
"Based on early reports from vote counting centres, it appears virtually certain that the results will be in favour of separation," Carter Center observer and former Tanzanian prime minister Joseph Warioba told reporters in Khartoum.
PROBLEM CASES
Preliminary results are expected by the end of the month and south Sudan would become an independent nation on July 9, according to the terms of the 2005 north-south peace deal that promised the referendum.
The EU mission said soldiers and intelligence officers had been stationed too close to voting centres in a few cases, raising the risk of intimidation.
Observers had raised concerns before the vote that there was a lack of informed discussion in the north about secession and in the south about unity.
"We were concerned that there wasn't a conducive environment for campaigning for unity in the south, similarly for secession in the north," the Carter Center's Sudan director Sanne van der Bergh told journalists.
Illustrating the strength of public emotion in favour of secession in the south, some voters expressed anger that even one person would vote for unity.
"I'm annoyed -- why are they voting for unity? I thought that we didn't have such people in the south -- they are not southern Sudanese," student Victor Ajuot, 25, said in Juba.
Senior north Sudanese official Ibrahim Ghandour told Reuters last week the voting, which ended on Saturday, had been "broadly fair", allaying fears that disagreements over the outcome would reignite conflict.
Sudan's north-south civil war began in 1955 and claimed an estimated two million lives before ending with a peace deal in 2005. (Additional reporting by Jason Benham in Juba and Ayman Samir in Cairo; Writing by Opheera McDoom; Editing by Jon Boyle)
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