Pro- al Qaeda group linked to consulate attack

A pro-al Qaeda group responsible for a previous armed assault on the U.S. Consulate in Benghazi is the chief suspect in Tuesday's attack that killed the U.S. ambassador to Libya, sources tracking militant Islamist groups in eastern Libya say.

 They also note that the attack immediately followed a call from al Qaeda leader Ayman al-Zawahiri for revenge for the death in June of a senior Libyan member of the terror group Abu Yahya al-Libi. The group suspected to be behind the assault -- the Imprisoned Omar Abdul Rahman Brigades -- first surfaced in May, when it claimed responsibility for an attack on the International Red Cross office in Benghazi.

 The following month the group claimed responsibility for detonating an explosive device outside the U.S. Consulate, and later released a video of that attack. Noman Benotman, once a leading member of the Libyan Islamic Fighting Group and now based at the Quilliam Foundation in London told CNN, "An attack like this would likely have required preparation. This would not seem to be merely a protest which escalated."