KHARTOUM (Reuters) - Nine south Sudanese opposition parties said on Tuesday they would challenge the election of the region's president and state governors in court, adding they had documented evidence of fraud.

The leader of the Sudan People's Liberation Movement (SPLM), Salva Kiir, won the presidential race in the south with 92.99 percent of the vote in the semi-autonomous region, which is expected to secede from the north after a referendum next year.

"The elections have been rigged," said Lam Akol, Kiir's only challenger who split to form a separate party last year. "We have documented evidence of the (army) taking over polling stations and arresting party agents."

Akol and eight other southern parties said in a joint statement that they would provide evidence to Sudan's Supreme Court to challenge the victory of Kiir and his party's governors in the country's first open polls in 24 years.

The SPLM said that while the elections in the north were rigged by President Omar Hassan al-Bashir's dominant National Congress Party, there was competition in the south and senior members of the SPLM had lost their seats in parliament.

"Senior political buro members of the SPLM lost their seats, but can you name one of the NCP leaders who lost theirs?" said Yasir Arman, a senior SPLM official.

The SPLM, a former rebel group which dominates the government of the oil-producing south, also lost the governorship of Western Equatoria state to an independent candidate.

Kiir said he felt "total dismay" at reports of fraud and promised to investigate.

International observers have said the elections across the country did not meet international standards but emphasized there had been intimidation by security forces in the south.

Sudan's north-south civil war, fuelled by ethnicity, ideology and oil, ended in 2005 with a peace deal between the SPLM and the NCP. The elections were supposed to be the climax of democratic transformation in Africa's largest country but few observers believe the polls achieved this goal.

The SPLM says Akol is an NCP agent in the south and accuses him of commanding an armed militia. Akol denies the charges. But he openly supported Sudan's President Omar Hassan al-Bashir in his successful re-election bid.

Bashir is wanted by the International Criminal Court for war crimes in Darfur.