ABUJA - Nigeria's former military ruler Ibrahim Babangida has formally declared his intention to seek the ruling party's nomination for the presidential election next year, a further blow to incumbent President Goodluck Jonathan.

"The ruling party accepts that all of us including Jonathan have the right to contest and I will exercise my franchise," Babangida said in a speech yesterday.

Babangida, pictured, seized power in August 1985 and ruled Nigeria for nearly eight years. He was forced to step down in 1993 after he annulled an election that was generally regarded as fair.

The declaration by Babangida, a Muslim from the northern Nigerian state of Niger, poses a further challenge to any ambition by Jonathan, a Christian from the southern Niger Delta, to seek re-election in the polls due in January.

Former Nigerian vice-president Atiku Abubakar, a Muslim from the northern Hausa ethnic group, also formally declared his intention on Sunday to seek the ruling party nomination.

An unwritten agreement in the ruling People's Democratic Party says power should rotate between the Muslim north and Christian south every two terms, meaning the next president should be a northerner if the principle is maintained.

Jonathan has not yet said whether he plans to stand, but a bid would need the support of northerners within the PDP to be guaranteed victory in the polls.

The presence of two northern candidates for the PDP primaries reduces his chances of winning their support.