Q+A-What are the consequences of Nigeria's bomb attacks?

LAGOS Oct 5 (Reuters) - Car bombs claimed by Nigeria's main militant group may not be the start of a crippling campaign of violence against the oil industry but they could pose a wider threat to political stability in the run-up to elections.

Following are some questions and answers about the bomb attacks, who could be responsible, and what the consequences might be for the oil sector and the political landscape.

WHO MIGHT BE RESPONSIBLE?

The bombs near a parade to mark Nigeria's 50th anniversary of independence were claimed by the Movement for the Emancipation of the Niger Delta (MEND), which carried out years of attacks on oil facilities until accepting an amnesty in 2009.

News outlets including Reuters received an emailed bomb warning about an hour before the explosions. It was sent from the same Yahoo! email address used by MEND to claim previous attacks and was signed Jomo Gbomo, the pseudonym used by the group's spokesmen in statements to the media.

South African prosecutors have charged Nigerian militant leader Henry Okah, who now lives in Johannesburg, with conspiracy to commit a terrorist act and the detonation of explosive devices in Abuja. His lawyer denied his involvement.

Security experts believe Okah was at one time the brains behind MEND, though he has denied ever being its leader.

But President Goodluck Jonathan has denied that the bomb attacks had anything to do with the Niger Delta, saying the perpetrators used the MEND banner as a cover.

He said a "small terrorist group" outside Nigeria -- an apparent reference to Okah -- carried out the attacks and was sponsored by "unpatriotic elements within the country".

The authorities suspect those close to Jonathan's main rival in elections due next year, ex-military ruler Ibrahim Babangida, may be involved. The secret service on Monday detained his campaign manager and questioned him about the attacks before releasing him on administrative bail without charge.

WHO ARE MEND?

MEND is basically a franchise under which a number of armed gangs led by warlord-like field commanders have operated in the creeks of the Niger Delta in recent years, blowing up oil pipelines, kidnapping oil workers and trading in stolen oil.

The group says it is fighting for a fairer share of the natural wealth in the delta, a vast network of mangrove swamps which is home to Africa's biggest oil and gas industry.

The region is one of Nigeria's poorest despite five decades of oil extraction, and its polluted swamps and villages -- most lacking electricity or clean water -- are perhaps Africa's most heinous example of the resource curse.

But MEND's carefully honed Robin Hood image -- struggling on behalf of impoverished villagers against oil firms and corrupt politicians -- belies a darker reality.

Some gangs under its banner were originally set up with backing from politicians to help rig elections. Its campaigns, far from improving the lives of ordinary Niger Deltans, have helped turned the region into a virtual military zone.

Its main field commanders, including Farah Dagogo, Government Tompolo and Ateke Tom, accepted amnesty last year, leading their followers to hand over weapons in return for promises of stipends and re-training.

Okah also accepted amnesty last year after gun-running and treason charges against him were dropped, but messages denouncing the amnesty continued from the Jomo Gbomo email account, believed to be written by Okah or his associates.

"Everyone in the structure knows Jomo Gbomo is Henry Okah. There is no MEND sitting anywhere in any camp. It's all Henry Okah, through and through," Jonathan's special adviser on the Niger Delta, Timi Alaibe, was quoted as saying.

The split between Okah and the commanders who accepted amnesty means it is unclear what capacity the group has left.

"Whoever is behind the Jomo Gbomo email, whether Henry Okah or someone else, would appear to be getting marginalised by the other militant leaders that were central to MEND," said Peter Sharwood-Smith, Nigeria manager for security consultancy Drum-Cussac.

WHAT ARE THE CONSEQUENCES?

MEND's attacks in early 2006 were its most spectacular, knocking out almost a quarter of Nigerian oil output in a matter of weeks. Sustained acts of sabotage over the next three years prevented the OPEC member's output from fully recovering, costing it an estimated $1 billion a month in lost revenues.

In an email to Reuters, Jomo Gbomo said the Abuja attacks had been "symbolic and opportunistic" and intended as a one-off high-profile reminder rather than the start of a renewed campaign of sabotage in the Niger Delta.

While further strikes against oil installations cannot be ruled out, security analysts see the prospect of sustained attacks with a significant impact on oil output as unlikely.

But the political consequences could be more severe.

MEND's claim for the attacks was an embarrassment for Jonathan, one of the main architects of the amnesty last year and the first Nigerian head of state from the Niger Delta.

The secret service's questioning of Raymond Dokpesi, Babangida's election campaign manager, has raised the stakes.

"Jonathan's political opponents are attempting to use the Abuja bombings to discredit him, alleging that the government ignored multiple warnings by both MEND and British intelligence given days in advance," intelligence firm Stratfor said.

"Dokpesi's arrest, meanwhile, is a sign that Jonathan suspects Babangida's camp of ties with Okah, and is the clearest sign yet that Jonathan is willing to play politics with the Abuja attacks as well."

The stand-off does not bode well for Nigeria as it prepares for elections already set to be the most fiercely contested since the end of military rule more than a decade ago. (For more Reuters Africa coverage and to have your say on the top issues, visit: af.reuters.com/ ) (Editing by Giles Elgood)