Nigerians voted amid tight security in a governorship election on Saturday in President Goodluck Jonathan's restive and oil-rich home state of Bayelsa, where last week militants attacked a major oil pipeline.

Nigeria's 36 state governors are some of the most powerful politicians in Africa's most populous nation, in some cases controlling budgets larger than other African countries and gubernatorial elections can stoke violence.

At least one person was killed and several injured at a pre-election rally on Tuesday in the southern Ijaw region in Bayelsa, witnesses said.

Ten thousand to 15,000 policemen are deployed for the election, these include anti-bomb squads from Delta, Edo and Rivers states to ensure that all key points are saved, said Chris Olakpe, Bayelsa's police commissioner.

We are going to effectively police all polling booths and normal patrols would go on to ensure miscreants do not hijack the process, added Olakpe, who took up his position this week.

Even with a huge police and military presence it will be difficult to guard all ballot boxes in Bayelsa, where thousands of kilometres (miles) of labyrinthine creeks weave through swamplands, sitting on top of billions of dollars of crude oil.

Soldiers, police are all over so I'm hopeful there will be no problem of shooting, killing, burning of houses and all that, said John Masi, a 35-year old labourer.

I want the new governor that will be elected today to quickly construct the new university so I can get work to do and make money to get out of this wooden shack and have a better life for my wife and two children.

Bayelsa is one of the three Nigerian states that make up the oil rich Niger Delta, where militant gangs held the government to ransom for years by sabotaging pipelines and stealing industrial amounts of oil until an amnesty in 2009.

Attacks have been rarer and less destructive since the amnesty but they still occur. Last week the Movement for the Emancipation of the Niger Delta (MEND), formerly Nigeria's main militant threat, claimed a strike on a pipeline owned by Italian firm Eni, which confirmed 4,000 barrels per day of output had been cut by the attack.

MILITANTS

Under the amnesty thousands of militants gave up their weapons, joined training schemes and drew stipends. Security sources say remaining gangs in the Niger Delta do not have the capacity to do the damage seen in the past, which at its height cut more than a third of the OPEC-member's output.

Several false threats purporting to be from MEND have been sent in the past and recent damage caused to Nigeria's oil infrastructure has been done by gangs stealing oil for illicit refining and sale, rather than the result of militant strikes.

Diplomats and security sources have said violence in the Niger Delta is often stoked by rival politicians and the race for the Bayelsa governorship post has been fierce.

Nigeria's Supreme Court removed Governor Timipre Sylva from his post last month because it said his tenure should have expired, replacing him with Bayelsa's speaker of the house of assembly.

The dominant ruling People's Democratic Party (PDP) didn't allow Sylva to run in its primary last November, the first time the PDP has stopped a sitting governor from seeking a second term. Thousands of soldiers were then deployed to Bayelsa, prompting outrage from Sylva's team.

The winner of that primary, Henry Dickson, is the clear favourite to win Saturday's vote. President Jonathan is backing Dickson and is travelling from the capital Abuja to his home state to cast his vote, the presidency said.

Western diplomats said Sylva was snubbed because he fell out with his former ally Jonathan. Sylva will not run in the election but is seeking to nullify the most recent PDP primary, hoping to revert back to the primary he won last year.

Bayelsa has a population of around 1.5 million, the least populous state in a country of more than 160 million but it is key to Nigeria's economy due to its substantial oil wealth.

(Additional reporting and writing by Joe Brock, editing by Rosalind Russell)