A bomb exploded in a military area in northern Nigeria Sunday night, killing 15 people just hours after Christian President Goodluck Jonathan was inaugurated.

Another 35 people were injured from the blast at the bar inside army barracks in Bauchi, Nigeria – a town that is a stronghold of the radical Muslim group known as Boko Haram (meaning “Western education is sacrilege”), according to The Associated Press. No group has yet claimed responsibility for the attack on the military.

The bombing is seen as a challenge to the authority of Jonathan, a Christian from the south, by those who want a Muslim president installed.

Jonathan became president of Nigeria last year when his Muslim predecessor, Umaru Yar’Adua, died from a long-time medical problem.

The Christian politician finished the remaining year of Yar’Adua’s term and was elected in April for another four years.

Muslims contend that a Muslim president needs to be elected according to the unwritten agreement that presidents will rotate between the country’s Christian south and Muslim north.

Nigeria, the most populous nation in Africa, is nearly evenly divided between Muslims in the north and Christians in the south.

Muslims complained that the votes for the presidential election were rigged, but independent observers said the election process was the fairest in decades.

More than 60 churches were burned and thousands of Christian-owned homes, destroyed in April after preliminary results indicated that Jonathan had won over Muslim candidate Muhammadu Buhari.

Responding to the post-election violence in April, Jonathan said, “Nobody’s political ambition is worth the blood of any Nigerian."

Last year, the extremist group Boko Haram, which has a history of violence against Christians, claimed responsibility for bombings in the city of Jos on Christmas Eve.

Those bombings killed dozens of people shopping in a busy market in a predominantly Christian neighbourhood.

Boko Haram also claimed responsibility for attacking several churches in Maidugari on Christmas Eve, killing six people.