Certainly Mossad has killed Mahmoud Al Mabouh. And this is not the new tactic. Mossad has frequently used the forged documents and disguised identities. Same method was employed in failed assassination attempt of Khalid Mashal in 1997. Well, many countries have called on israeli ambassadors for explanation like UK(whose 11 citizens were involved) and France. But at the end Moassad will get away with this bacuase there are no concrete evidences yet.
There is pressure from Dubai to act against Mossad as tourism is the lifeline of Dubai's economy.

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Whatever mind can conceive,it can achieve - W.Clement Stone