The summit comes as Nigeria's military pushes deep into Boko Haram's Sambisa Forest stronghold after recapturing swathes of territory.
Nigeria was on Saturday hosting talks on Boko Haram with regional and Western powers, as the United Nations warned of the terrorists' ties to ISIS group and its threat to African security.
Leaders from Benin, Cameroon, Chad and Niger were among the delegates, alongside French President Francois Hollande, and high-ranking diplomats from the United States, Britain and the European Union.
Nigeria is seeking closer military cooperation to bring to an end nearly seven years of violence in the remote northeast, which has left at least 20,000 dead and displaced more than 2.6 million people.
The UN Security Council on Friday said the talks should help develop "a comprehensive strategy to address the governance, security, development, socio-economic and humanitarian dimensions of the crisis".
But it also expressed "deep concern" at Boko Haram's threat to security in West and Central Africa and "alarm at... linkages with the Islamic State" group in Syria and Iraq.
Boko Haram's shadowy leader Abubakar Shekau pledged allegiance to his ISIS counterpart Abu Bakr al-Baghdadi last year, although there has since been little evidence so far of direct support on the ground.
France's Hollande, who arrived in Abuja late on Friday from the Central African Republic, met his Nigerian counterpart Muhammadu Buhari at the presidential villa before the start of the summit.
Both countries recently signed an agreement on closer military cooperation, including intelligence sharing, and France is keen to help implement a regional solution to the insurgency.
Paris has traditionally concentrated on its former colonies surrounding Nigeria and sees itself as well-placed to help closer ties and longer-term economic development in the troubled region.
'Defeat' cautionThe summit -- two years after a first such high-level gathering in Paris -- comes as Nigeria's military pushes deep into Boko Haram's Sambisa Forest stronghold after recapturing swathes of territory.
Former military ruler Buhari has vowed to defeat Boko Haram before the end of his first year in office later this month and the army has portrayed the Islamists as in disarray.
But there have been warnings against any premature declaration of victory.
Deputy US Secretary of State Anthony Blinken said Washington, which is flying surveillance drones over northeast Nigeria from a base in northern Cameroon, did not see Boko Haram as defeated.
But he conceded "they have been degraded" and said the US was "extremely vigilant" about the connections, amid reports of Boko Haram rebels fighting in lawless Libya and the group's ties to Al-Qaeda affiliates in the wider Sahel region.
"This is again something we are looking at very, very carefully because we want to cut it off," he told reporters in Abuja on Friday.
Regional forceThe formal deployment of a long-awaited 8,500-strong regional force comprising troops from Nigeria, Benin, Cameroon, Chad and Niger is expected to be high on the agenda at the talks.
The African Union-backed force, based in Chad's capital N'Djamena under a Nigerian general, was supposed to have been on the ground in July last year.
Plugging gaps and improving coordination between armies that are currently operating largely independently is seen as vital, with Boko Haram now thought to be in remote border areas on and around Lake Chad.
Lake Chad forms the border between Nigeria, Cameroon, Chad and Niger.
With Boko Haram on the back foot, attention has turned to the plight of the displaced. Two million Nigerians have been internally displaced and are living in host communities or camps.
The government of Borno state -- the worst-hit by the violence -- has said the displaced face a "food crisis" and $5.9 billion (5.1 billion euros) was needed to rebuild shattered infrastructure.
US ambassador to the UN Samantha Power, who visited northeast Nigeria and northern Cameroon last month, said 9.2 million people in the wider region were affected by the conflict.