Afghan police officers inspect the site of a blast in the central province of Ghazni, Afghanistan, Saturday, June 18, 2011. Two roadside bomb attacks on Saturday killed four private security guards escorting supply convoys for a NATO base in eastern Afghanistan, a police chief said. (AP Photo/Rahmatullah Nikzad)

Photo by: Rahmatullah Nikzad

Afghan police officers inspect the site of a blast in the central province of Ghazni, Afghanistan, Saturday, June 18, 2011. Two roadside bomb attacks on Saturday killed four private security guards escorting supply convoys for a NATO base in eastern Afghanistan, a police chief said. (AP Photo/Rahmatullah Nikzad)