Nigerian President Goodluck Jonathan said on Sunday he sacked his defense minister and national security adviser last week because the government needed new anti-terrorism tactics.
Militant Islamist sect Boko Haram has been fighting an insurgency against Jonathan's government since he entered office over a year ago. Several military crackdowns and a state of emergency have failed to stem the violence.
The presidency issued a statement on Friday saying Jonathan's two top security chiefs had been dismissed but did not give a reason why.
"We think some new persons have to come in to change tactics in our fight against terrorism.... It's not that they were not working but just that we need to change tactics," Jonathan said in a meeting with reporters aired on state television on Sunday.
Boko Haram, which is based in the remote northeast, has rapidly overtaken militants in the oil-producing southern Niger Delta as the country's biggest security threat.
Niger Delta militants gave up arms in return for training and stipends in a 2009 amnesty but brief efforts to hold a dialogue with Boko Haram earlier this year failed.
"Boko Haram has no face and government will not dialogue with a faceless people. They must come out and tell us why they are doing what they are doing," said Jonathan.
Gun and bomb attacks blamed on Boko Haram have killed hundreds since the movement started its uprising more than two years ago.
It is fighting to carve out an Islamic state in Nigeria - a country nearly evenly split between Muslims and Christians. Attacks on churches have intensified this month, sparking deadly religious violence in northern Kaduna state.
(Reporting by Felix Onuah; Writing by Joe Brock; Editing by Ralph Gowling)