http://www.haaretz.com/hasen/spages/628577.html<snip>
"The explosions were believed to have been set off when a pickup truck carrying masked militants and laden with weapons blew up. Palestinian security officials said the blast was apparently caused by the mishandling of explosives.
Palestinian Authority Chairman Mahmoud Abbas' Fatah faction placed the responsibility for the explosions with Hamas. "The Fatah Central Committee holds the Hamas movement fully responsible for the victims of the military parade (that was held) among civilians," the committee said in a statement.
But in a press conference several hours after the incident, Hamas officials claimed that the rockets displayed during the rally were dummies that did not contain explosives. They also slammed the Palestinian Authority for blaming Hamas for the blasts."
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"Israel Defense Forces officials denied involvement in the incident, which took place only hours after Islamic Jihad militants in Gaza Strip fired several Qassam rockets at Israel, causing no injuries or damage."