| WARRI, Nigeria
WARRI, Nigeria A governorship election in one of Nigeria's main oil-producing states got off to a slow start on Thursday, with some people left off voter lists and isolated attempts to sabotage election materials.
Thousands of armed police and soldiers have been drafted to Delta state, which is holding a re-run after a court last year overturned the 2007 election of governor Emmanuel Uduaghan, a member of the ruling People's Democratic Party (PDP).
Delta is one of three main states in the Niger Delta, the heartland of Africa's biggest oil and gas industry and a restive region seen as a potential flashpoint during presidential and parliamentary elections in April.
Thursday's vote is seen as a litmus test for the conduct of those nationwide polls.
Electoral commission officials said all voting materials had been dispatched and polling stations in some areas opened shortly after 12:00 (1100 GMT) as planned, although not all voters could find their names on the electoral roll.
"This is where I registered but I can't find my name on the list," said one voter, Johnson Eteme, at a polling station in Warri, the main oil city in the state.
A Reuters correspondent and other local journalists saw a group of unarmed youths attempt to hijack a minibus carrying electoral materials in the center of Warri shortly before polling began. The journalists were chased away by the mob.
Around 25,000 police officers, including armed anti-riot police, as well as soldiers and bomb disposal experts are on hand to try to ensure the vote passes off peacefully.
President Goodluck Jonathan, who is from the Niger Delta, flew down from Abuja on Tuesday to support Uduaghan's campaign. But Uduaghan is not a universally popular figure and security experts fear unrest if he is declared winner of the polls.
The run-up to voting in Delta has already been marred by disputes over the voter register, leading to an attack on the local office of the electoral commission.
WAVE OF VIOLENCE
Nigeria has been shaken by violence in recent weeks, including a New Year's eve bomb blast on the edge of an army barracks in Abuja a week after a series of blasts and subsequent clashes killed 80 in the central city of Jos.
Homemade bombs hit a political rally in Bayelsa state, next to Delta, on December 29 and there are fears that the oil region could flare up again ahead of the April polls.
Warri was hit by twin car bombs last March during talks about implementing an amnesty program for militants brokered by Jonathan.
Jonathan is the first Nigerian president from the Ijaw ethnic group, the largest in the Niger Delta, and his failure to win the ruling party primaries next week or the April polls could trigger unrest in his home region.
But his election bid is contentious because he is a southerner. Some in the ruling party say an agreement about power sharing among Nigeria's regions meant the next president should be a northerner.
The PDP has been the dominant party in Nigerian politics since the end of military rule just over a decade ago, controlling more than two thirds of the country's 36 states.
But several PDP governors including Uduaghan have had their 2007 elections overturned by the courts in recent months.
The polls four years ago were so marred by violence and intimidation that observers declared them not to have been credible and legal wrangling dragged on in some cases for years. Nigeria is hoping to avoid a similar fiasco in April.
Uduaghan faces 13 challengers including Great Ogboru of the Democratic People's Party and Ovie Omo of the Republican Party of Nigeria, seen as his two main rivals.
(For more Reuters Africa coverage and to have your say on the top issues, visit: af.reuters.com/)
(Writing by Nick Tattersall; Editing by Jason Neely)