Bessler spoke on a rooftop, overlooking the sprawling Jalozai refugee camp in western Pakistan.

CNN: Displaced Pakistanis crowd camps as they flee fighting

"Last year ... 4 million people worldwide lost their homes, out of which you have half a million displaced in Pakistan, " said Manuel Bessler, a top U.N. official in Islamabad.

CNN: Displaced Pakistanis crowd camps as they flee fighting