ABUJA, Nigeria — The United States and British governments are warning that the Boko Haram extremist group is actively planning to kidnap foreigners in northeast Nigeria.

The British warning says the extremists are targeting Western foreign workers in the Bama area of Borno state, close to the Cameroon border.

The Nigeria-based Boko Haram has been pushed out of strongholds by military efforts but continues to control parts of the country’s northeast.

That has challenged aid groups’ efforts to address a hunger crisis that the United Nations says has left 4.7 million people in urgent need of food aid.

Nigeria is part of what the U.N. has called the largest humanitarian crisis since the world body was founded in 1945. The World Food Program has warned of aid cuts if more help doesn’t arrive.