Two groups claimed responsibility in the early evening hours , local time : the Mujahedeen of Egypt and the Abdullah Azzam Brigades . In its statement , the latter group said the attacks were in retaliation for the government 's clampdown on dissidents in the wake of the Sinai Peninsula bombings of October 2004 . In the early hours of Sunday , 1 May , security forces arrested some 225 individuals for questioning , mostly from the dead three 's home villages and from the area where they lived in Shubra . Particularly keenly sought was Muhammad Yassin , the teenage brother of Ehab Yousri Yassin , whom the police described as the only remaining suspect in the bazaar bomb attack and a material witness to the Saturday afternoon shooting . Muhammad was later extradited from Libya
Sinai Peninsula bombings
2004 Sinai bombings
April 2005 Cairo terrorist attacks