Attacks on aid workers around the world appear to be increasing, according to People in Aid.
Last week, five workers with Medecins Sans Frontieres were killed in an attack by unknown assailants in Afghanistan.
Two Afghan nationals were killed as well as a Belgian, Norwegian and Dutchman.
Jonathan Potter, chief executive of People in Aid, which encourages good practice in the treatment of aid workers, said: "We don't keep a tab but we are hearing about more deaths, particularly in Iraq and Afghanistan."
He said that aid agencies faced an agonising choice in whether to pull out staff and cut off vital supplies of aid, or put staff at risk.
"In one Afghan village, there were two western aid workers. The locals wanted them to stay, but there was an explosion outside their house and they were withdrawn. It's a very tough choice - 30,000 people aren't going to get what's on offer for the sake of two aid workers."