* Nigeria to elect governors for its 36 states this week
* Hundreds killed in election violence in the north
* Powerful governors control huge budgets
By James Jukwey
ABUJA, April 26 (Reuters) - The final stage in Nigeria's long election process begins on Tuesday with fiercely contested state governorship polls to be held from the southern oil delta to the Muslim north, where hundreds have been killed in unrest.
Violence erupted in the north last week after Goodluck Jonathan, a southern Christian, was declared winner by a wide margin of an April 16 presidential election.
Supporters of his northern opponent Muhammadu Buhari rejected the results and took to the streets. Hundreds of people died in the ensuing violence and churches, mosques and homes were set ablaze.
Thousands of displaced people are sheltering in army barracks where they are being looked after by aid agencies.
Some suggested this week's voting for state governors and state assemblies be postponed to allow tempers to cool but Jonathan said the polls would go ahead despite the violence.
"This was a public declaration that he won't let anything stand in the way of completing this election cycle," Patrick Mmeme, a public policy analyst and writer, told Reuters.
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State polls have in the past led to unrest in the Niger Delta, the southern heartland of Africa's biggest oil and gas industry, where politicians armed thugs to intimidate voters.
There has already been violence in some parts of the region, including rioting in the state of Akwa Ibom and attacks on rallies in Bayelsa, and the security forces are on high alert.
But this year it is the north which provides the biggest security headache. In two northern states, Kaduna and Bauchi, where some of the worst violence took place last week, voting will be delayed until Thursday.
"The north has become a killing field as a consequence of growing social, ethnic and religious intolerance," Abdullahi Adamu, a former state governor elected senator for Nasarawa West in the region, told the Daily Trust newspaper.
"Violence has drawn the north back several decades. We have murdered our brothers and sisters in cold blood, destroyed our property and even infrastructure and places of worship for no just cause," said Adamu, a prominent member of Jonathan's party.
Some commentators have expressed shock that rioters attacked the palaces of emirs, traditional Muslim rulers, in a part of the country where authority was once respected.
Properties of northern politicians and businessmen known to have backed Jonathan, who became president when his predecessor died, are also reported to have been attacked.
Nigeria, Africa's most populous country, with more than 150 million people, is split almost equally between a mainly Muslim north and a majority Christian south, although large minority groups live in both regions.
As in much of Africa, losers are often unwilling to concede defeat and wait in opposition for another four or five years while the winner enjoys all the trappings of power.
Despite providing more Nigerian leaders than the south since independence from Britain 50 years ago, the north remains mired in deeper poverty than anywhere else.
The series of elections began with a parliamentary vote which was delayed by administrative chaos, followed by the presidential ballot. This week's polls will again be fiercely contested by all five main parties.
Much is at stake in the finale since the 36 state governors control big budgets in the oil-producing country, are closer to the people and influence policy at state and federal level.
A successful conclusion of the elections, judged so far to have been the most credible since a return to democracy in 1999, could boost Nigeria's world standing and attract investment. (Editing by Andrew Dobbie and Nick Tattersall) (For full Reuters Africa coverage and to have your say on the top issues, visit: af.reuters.com/ )