Tunisia bus bomber arrested, freed before attack

By Tarek Amara and Mohamed Argoubi TUNIS (Reuters) - The suicide bomber in Tunisia who blew himself up in a bus packed with presidential guards on Tuesday had been arrested by police before on suspicion of jihadist ties but was released for lack of evidence, a security official said. Tunisia, one of the Arab world's most secular nations, is struggling to counter Islamist militancy since becoming a beacon of democratic change in the region after its 2011 uprising that ousted autocrat Zine Abidine