I have no mod point but if somebody can, please mod this up. Writing that the MEK is an assassination arm of the Mossad is just repeating Iranian government propaganda. They are a Marxist movement that was fighting the Shah before the revolution and has been forced into exile by the islamists after the revolution. As one of the political opponent of the islamist government in Iran, they may have received support from countries opposing the iranian government (although I am not aware that they ever received specific help from Israel). But they are certainly not affiliated to Mossad.
They have sponsored violent actions in the past, but they are not considered a terrorist movement in Europe anymore ( although they still are in the US)