A main al Qaeda-linked group said it was behind a suicide bombing in northeastern Iraq on Saturday, and vowed more bloody attacks during Sunday's election, according to an Internet statement. "A lion from the martyrs brigade of the Al Qaeda Organisation for Holy War in Iraq attacked the Americans and their agents in Khanaqin," said the statement from the group led by Abu Musab al-Zarqawi, al Qaeda's leader in Iraq, posted on an Islamist Web site. "For the last time, we warn that tomorrow will be bloody for the Christians and Jews and their mercenaries and whoever takes part in the game (election) of America and (Interim Prime Minister Iyad) Allawi," it said. The U.S. army said a suicide bomber blew himself up outside a U.S.-Iraqi military centre in the town of Khanaqin near the Iranian border, killing at least three Iraqi soldiers and five civilians. The army said the blast was outside the protective walls of the military centre, which was continuing to function as normal. Local officials said the bomber had walked up to the centre wearing explosives and blown himself up. Zarqawi, appointed by Osama bin Laden as his top deputy in Iraq, has claimed responsibility for some of the grisliest hostage beheadings and suicide bombings to hit the country.