From the second paragraph of this article:

...An indictment was issued yesterday against Islam Farhi Jibril of Gaza for transporting an explosives belt in a Red Crescent ambulance. The charges state that on March 27, Jibril attempted to smuggle from Gaza to Ramallah an explosives belt of the type used by suicide bombers. He used his sister-in-law and her children to act as "emergency patients" on their way to the hospital. A collaborating dentist came along as the "doctor." Israeli checkpoint soldiers were suspicious, however, and upon inspecting the ambulance, they found the explosives hidden under a stretcher upon which laid Jihad’s nephew. The driver had received the belt from al-Aqsa Martyrs Brigades terrorists...

This is not the only example I have seen of this tactic.

Details of the effects of the carefully constructed suicide fragmentation bombs can be found in this article.