Donor countries meeting in Oslo on Friday pledged $672 million in emergency aid for people threatened by famine in the Lake Chad region, Norway's Foreign Minister Borge Brende said.
The amount was pledged over three years, and aims to help 10.7 million people in need. The international donor conference in the Norweigian capital aims to raise $1.5 billion in 2017 for the region, the United Nations said.
UN Under-Secretary General Stephen O'Brien said he was optimistic the overall target for this year would be met.
"In one morning we have raised a third of that," he said.
The United States, whose new administration has said it intends to slash its development aid budget, was not among the 14 countries that pledged money.
Lake Chad region
The region comprises northeast Nigeria, northern Cameroon, western Chad and southeast Niger.
An eight-year conflict between the Nigerian army and Boko Haram militants has devastated the region.
The situation in the region has been described by Doctors Without Borders (MSF) as "the worst in the world."
Humanitarian organisations can only access populations at risk as the Nigerian army liberates territories from Boko Haram, but people remain inaccessible.
Many roads are passable only under the escort of Nigerian soldiers, and ambushes pose a constant threat. Other places are accessible only by helicopter, where "horrible rates of malnutrition" are observed among children.
"In the whole of the Lake Chad region we've seen the fight against Boko Haram take priority above all else, with military and political objectives directed towards this," said Natalie Roberts, head of emergencies for MSF in Nigeria's Borno State.
"We now find ourselves in the midst of a huge humanitarian crisis," she added.