(Reuters) - A small terrorist group based outside Nigeria and not militants from the oil-producing Niger Delta carried out last week's car bomb attacks in the capital Abuja, President Goodluck Jonathan said on Sunday.
Two car bombs exploded near a parade marking Nigeria's 50th anniversary of independence on Friday, killing at least 10 people and injuring 36, according to the police.
The attacks were claimed by Nigeria's main militant group, the Movement for the Emancipation of the Niger Delta (MEND).
A MEND statement signed Jomo Gbomo -- the pseudonym used by the group to claim previous attacks on Nigeria's oil industry -- was emailed to media warning the area should be evacuated an hour before the Abuja bombs went off.
But Jonathan said investigations had revealed MEND members knew nothing about the attacks and they had been carried out by a small group based outside Nigeria, sponsored by "unpatriotic elements within the country."
"It is a small terrorist group that resides outside Nigeria that was paid by some people within to perpetrate the dastardly act," Jonathan said, according to a statement from his office.
"We are on their trail and I promise Nigerians that the matter will be investigated to the last. Until everybody is brought to book, we will not rest."
The Nigerian police said it had made one arrest in connection with the attacks and declared two other men -- named as Chima Orlu and Ben Jessy -- wanted, saying they were suspected to be the "masterminds" of the plot.
Nigeria's secret service has said it received foreign tip-offs ahead of the attacks and had stepped up security accordingly, including towing 65 vehicles from the streets and cordoning off roads leading to the parade ground.
Jonathan said on Saturday those responsible had used the MEND name to "camouflage criminality and terrorism."
SENIOR MILITANT ARRESTED
Henry Okah, a senior MEND figure, was arrested in South Africa on Saturday under counter-terrorism laws and was due to appear in court in Johannesburg on Monday, his lawyer said.
"The warrant of arrest alleges that he contravened the Protection of Constitutional Democracy Against Terrorist and Related Activities Act ... He totally denies any wrongdoing anywhere," Okah's lawyer Piet du Plessis told Reuters.
Security experts believe Okah -- who accepted a government amnesty last year after gun-running and treason charges against him were dropped -- was at one time the brains behind MEND, although he has denied ever being its leader.
Jonathan's special adviser on the Niger Delta, Timi Alaibe, was quoted on Sunday as saying MEND's leaders were cooperating with the government and that Okah was using the group's name.
"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," he was quoted as saying by the This Day newspaper.
MEND carried out attacks on oilfields and pipelines in the Niger Delta, home to Africa's biggest oil and gas industry, for years until accepting an amnesty in 2009.
It has said it is fighting for a fairer share of the natural wealth for the vast wetlands region, whose villages remain mired in poverty despite five decades of crude oil extraction.
But MEND has always been a nebulous organization and the line between militancy and criminality has long been blurred.
Many of the gangs that carried out attacks in the group's name were originally set up as sabotage squads to help rig elections, rights groups and security analysts say.
They went on to thrive on a lucrative trade in stolen oil and on kidnapping for ransom and effectively work as guns-for-hire, security experts say.
Jonathan inherited the presidency this year after the death of President Umaru Yar'Adua. One of his main achievements while serving as Yar'Adua's deputy had been helping to cement the amnesty deal in the Niger Delta.
He faces an election next year and some analysts have questioned whether the Abuja bombs were intended to undermine his credibility by showing the Niger Delta issue is unresolved.
"(The bombing) has nothing to do with the amnesty, but it has everything to do with politics," Jonathan advisor Alaibe said.