Sacrificing the self by suicide bombing complies neither with Qur’an nor the practices of the Messenger. Opinions delivered by scholars that support suicide bombing are not based on strong evidences and are unacceptable. Suicide bombing is different than defending own religion and country. It is also forbidden, since it is a way to take a human’s life without God’s permission.
Please also see:
Is terrorism part of Islam? http://www.islamandquran.org/?p=3609
What is the ruling on suicide? http://www.islamandquran.org/fatwas/ruling-on-suicide.html