U.N. Security Council was heading to West Africa on Wednesday night to examine the threat posed by Boko Haram to the countries most affected by the Islamic extremist group - Nigeria, Niger, Chad and Cameroon, all four of which also face a serious humanitarian crisis.

France's U.N. ambassador, Francois Delattre, told reporters that "this is the first time ever that the Security Council will visit the region" and members want to support those four countries "in their fight against terrorism."

In Nigeria, a seven-year uprising by Boko Haram has killed more than 20,000 people and driven 2.6 million from their homes, and the extremist group has moved into the three neighboring countries. A U.N. humanitarian coordinator said last month that malnutrition in Nigeria's northeast was so pronounced that some adults were too weak to walk and some communities had lost all their toddlers.

Council members were flying to Cameroon's capital, Yaounde, where their initial meetings were scheduled to start Friday. They then plan to go to Chad and Niger, then on to Nigeria, where they will also visit a camp in the north for people displaced by Boko Haram.

Delattre said the council will be encouraging the governments to facilitate access for humanitarian aid and to adopt "a comprehensive approach to address the root causes of terrorism."

British Ambassador Matthew Rycroft said council members will engage leaders of the four countries on what they are doing in response to Boko Haram and on how they are coming together "to tackle what is clearly a cross-border threat."

"This is not just terrorism in one box," with development, good governance, the environment, climate change and the humanitarian crisis in separate boxes, Rycroft said.

"Everything is interconnected," he said. "The golden thread between good governance, justice, civil society, the role of development flows straight into preventing conflict, so we want to make sure we have a broad view of all of the factors at play."

At a donor conference last week in Oslo, U.N. humanitarian chief Stephen O'Brien said 14 countries had pledged $672 million over the next three years to prevent a famine in the four African countries around the Lake Chad basin.

O'Brien said in a telephone briefing to U.N. reporters from Yemen's capital, Sanaa, that the pledges include $458 million for 2017 - about a third of the $1.5 billion needed. He described that as a "very positive and a good news story." He said several other countries indicated they would pledge later this year and the U.N. also expects a contribution from the United States.

AP