Raymond Dokpesi, the director of Babangida’s campaign for 2011 presidential elections, was questioned by the secret service on Monday after last Friday’s car bombs near a parade to mark Nigeria’s 50th anniversary of independence.

The investigation into the blasts, which killed at least 10 people and injured scores more, risks becoming a divisive issue ahead of presidential elections next year in which President Goodluck Jonathan and Babangida are so far the two main rivals.

“The president has said let the authorities finish their investigation,” Ken Saro-Wiwa, Jonathan’s special assistant on international affairs, told Reuters.

“Anyone who has who has been invited for questioning has to deal with those questions, because the intelligence is not just coming from Nigeria but from British and US intelligence sources as well,” he said.

Dokpesi was released without charge late on Monday on administrative bail, meaning he could be recalled for further questioning by the State Security Service (SSS), officials said.

“We believe this is a political witch hunt. The government of the day is becoming intolerant of the opposition viewpoint,” Babangida’s campaign spokesman Kassim Afegbua told Reuters.

The attacks were claimed by the Movement of the Emancipation of the Niger Delta (MEND), the main militant group in the nation’s southern oil heartland, but Jonathan — who is from the region — has said the group’s name was used as a cover.

Former MEND field commanders and scores of their followers, among the thousands to have accepted amnesty last year, met Jonathan in the presidential villa and condemned the bombings.

“We are not part of the incident ... MEND is not involved,” said Government Tompolo, one of the group’s former commanders.

MEND has always been factionalized and some die-hard militants have dismissed those who took amnesty as sell-outs.

Prosecutors in Johannesburg on Monday charged Henry Okah, long a senior figure in MEND who now lives in South Africa, with conspiracy to commit a terrorist act and the detonation of explosive devices in Abuja. His lawyer denied his involvement.

State television said late on Monday Dokpesi had been held for questioning over text messages found on the phone of a main suspect in the bombings, which referred to a monetary payment.

“Since MEND has owned up, we find it very curious that the government is chasing other avenues,” Afegbua said.

The presidential election in Africa’s most populous nation had been due in January but has been pushed back to April, ostensibly to give electoral authorities more time to prepare.

It was already shaping up to be the most fiercely contested since the end of military rule a decade ago, with no consensus candidate in the ruling People’s Democratic Party (PDP) and division over whether the nominee should be from north or south.

The debate hinges on an unwritten pact in the ruling party that power rotates between the main regions every two terms.

Jonathan, a southerner, inherited the presidency when northerner Umaru Yar’Adua died this year part way through his first term. His backers say he was elected on a joint ticket and can complete the second term; but his opponents, including northerner Babangida, say the agreement must stand.

The apparent suspicion that Babangida’s camp could be involved in the Abuja bombs has raised the political stakes.

Al Jazeera broadcast comments from Okah in detention in South Africa in which he accused a presidency official of asking him to blame the bomb attacks on northern politicians. Jonathan’s office challenged him to name the aide involved.

“A lot of mud has been thrown but this matter is not best judged in the court of public opinion,” Saro-Wiwa said.

MEND’s claim of responsibility was an embarrassment for Jonathan, who was one of the main architects of last year’s Niger Delta amnesty and who is the first Nigerian leader to come from the vast wetlands region.

Jonathan has said the attacks had nothing to do with the Niger Delta. He has blamed a “small terrorist group that resides outside Nigeria” — an apparent reference to Okah — and said it was sponsored by “unpatriotic elements within the country.”