Nigeria's government is conducting an investigation into reports of a possible coup plot.
Government spokeswoman Remi Oyo said Friday Nigerian authorities are investigating what she called allegations of serious breaches of security within the country's armed forces.
But, she says, intelligence officials are simply doing their job, and she insisted that President Olusegun Obasanjo remains in firm control.
"Let me say that President Olusegun Obasanjo trusts the security agencies and officials of government," she said. "He believes in the Nigerian people. He knows that the Nigerian people believe in democracy and will continue to work for and with democracy and what the intelligence community is doing is not anything extraordinary, it's all in its job."
Military officials say nearly 30 mid-ranking officers, most of them from the mainly Muslim Hausa-speaking north, have been interrogated and that their cell phones have been impounded.
Nigerian newspapers are reporting they were possibly plotting a coup and were trying to enlist the support of other soldiers, disgruntled by general insecurity, corruption and frequent irregularities in elections.
One man identified as a possible leader of the plot, former major Hamza al-Mustapha, was taken from the high security Kirikiri jail in Lagos this week to face questioning.
Mr. Mustapha is awaiting trial for the 1996 attempted murder of a newspaper publisher. He was responsible for the security of military ruler Sani Abacha, who died while still in power in 1998.
President Obasanjo, himself a former military ruler, is a Christian from the southwestern ethnic Yoruba group. He returned to power in 1999 through the ballot box and won a second term last year, marking the first democratic transition in Nigeria's post-colonial history.