Photograph by: KHALIL SENOSI
" I think the rigging will have a negative impact on the referendum. If people remain silent in the face of this cheating, the referendum itself will be rigged " Jacob Zuma
"The elections were rigged and the percentage of the votes obtained by the president of south Sudan shows this," said Lam Akol, who broke away from Kiir's Sudan People's Liberation Movement last year to form the SPLM- Democratic Change (SPLM-DC).
Kiir was declared winner on Monday with 92.99 percent of the votes. Akol, a former foreign minister, was a distant second at 7.01 percent.
The SPLM clinched nine out of the 10 gubernatorial posts in south Sudan, with Eastern Equatoria state electing an independent.
It also took control of the vast majority of seats in the southern national assembly, according to partial results.
"We totally reject these results," Bona Malwal who heads the Democratic Forum, a small southern opposition party, said during a news conference with Akol.
Only voters registered in south Sudan were able to vote for the leadership of their autonomous government, as well as for legislative representatives in the southern parliament and southern governors.
Akol, who lives in Khartoum, could not vote for himself in the election.
Some 10 million Sudanese, including 2.8 million southerners, voted between April 11-15 in the country's first multi-party election in 24 years.
It was also the first competitive election for the south Sudanese presidency and national assembly, institutions born out of a 2005 peace deal between north and south Sudan to end a brutal decades-long war.
The peace deal also provides for a referendum in January 2011 on whether southerners want to break away from the north or remain part of a united Sudan.
"I think the rigging will have a negative impact on the referendum. If people remain silent in the face of this cheating, the referendum itself will be rigged," Akol warned.
European and American election observers said the election had failed to reach international standards, and pointed out "weakness" of the organisation in the south.
Observers said they hoped the logistical and technical delays that marred the election would be avoided in the referendum.