The Nigerian army have entered Sambisa Forest, thought to be Boko Haram's last stronghold.
Warplanes lead offensive into Sambisa forest, 100 km from village where Boko Haram abducted 200 girls last year.
Children face abduction and conscription by the extremist group, which has killed an estimated 1,000 people this year.
Chad and Niger military leaders pledge to fight "side by side" with Nigerian army against Boko Haram.
"President Jonathan was a worthy opponent and I extend the hand of fellowship to him," said Buhari.
Buhari ahead with five states to go, but result could change with Niger Delta yet to declare.
There is still time for a reversal of fortunes, with some of President Goodluck Jonathan's big support bases in the oil-producing Niger Delta yet to report.
Opposition party rejects outcome in oil-rich state as closest presidential contest in a decade reaches climax.
All Progressives Congress in Rivers state accuses supporters of President Goodluck Jonathan of being behind killings of its campaigners.
PDP and APC parties are engaging in 'politics of the belly' to woo voters before tomorrow's poll.
More than 1.2 million people have been displaced within Nigeria and almost 200,000 have fled.
Two hundred vehicles transporting troops have entered northeastern Nigeria to take on the Islamist militants.
Jihadists attempt to sneak out of Baga town wearing women's clothes as the military campaign escalates.
APC leader to hold meetings with 'key members of the British establishment' to boost confidence.
He also said that the security reasons for the postponement of the election were 'flimsy'.
The group have encircled the northeastern city of Maiduguri for an assault ahead of the presidential vote.