Gunmen kidnapped four foreign aid workers from the Dadaab refugee camp in Kenya on Friday. Employees of the Norwegian Refugee Council from Canada, Norway, Pakistan and the Philippines were taken when their convoy was attacked inside Dadaab, considered the largest refugee camp in the world.

Dadaab lies near Kenya's border with Somalia, and members of the Somali rebel group al Shabab have carried out attacks and kidnappings in Kenya in the past. In October, two Spanish doctors were kidnapped from Dadaab and are still being held. Weeks earlier, three tourists from France and England were captured by al Shabab in Kenya.

To stop the violence at its doorstep, Kenya has sent forces into Somali to push al Shabab east.