From wikipedia:
http://en.wikipedia.org/wiki/False_flag
False flag operations are covert operations conducted by governments, corporations, or other organizations, which are designed to appear as if they are being carried out by other entities. The name is derived from the military concept of flying false colors; that is, flying the flag of a country other than one's own. Terrorist attacks may sometimes be in fact false flag operations, as in the Italian strategy of tension in which several bombings in the 1970s, attributed to far-left organizations, were in fact carried out by far-right organizations cooperating with the Italian secret services. Elsewhere in Europe, the Mouvement d'Action et Défense Masada, supposedly a Zionist group, was really a neo-fascist terrorist group which hoped to increase tension between Arabs and Jews in France. In 2005 in Basra, Iraqi police detained British soldiers from the Special Reconnaissance Regiment. They claimed that the soldiers were firing at Iraqi security forces and intent on planting bombs in false flag manner. The soldiers were unceremoniously released by British Army destruction of the cell block they being were held in [1].