An Israeli military aircraft fired a missile at a car in Gaza City on Wednesday (November 8), killing two Palestinian militants, a Palestinian security source said. The source identified the dead men as members of al-Aqsa Martyrs Brigades, an armed wing of President Mahmoud Abbas's Fatah faction. But Islamic militant group Hamas later claimed them as its own. The Israeli military had no immediate comment. Hamas and Al-Aqsa Martyrs Brigades are among militant groups spearheading a more than 6-year-old Palestinian uprising against Israel. Meanwhile, Palestinian President Mahmoud Abbas met Palestinian factions on Wednesday (November 8). Earlier, Palestinian President Mahmoud Abbas spoke of a "horrible and ugly massacre". He met with Prime Minster Ismael Haniyeh and various other Palestinian factions in his Gaza headquarters. Khaled Meshaal, leader of the governing Islamic militant group Hamas, urged retaliation. Hamas declared a partial truce in March 2005, which expired at the end of last year. It has not carried out a suicide bombing in Israel since 2004. The shelling was condemned across Europe and the Middle East. But an initial response by the United States stopped short of reprimanding Israel, whose prime minister, Ehud Olmert, is due to meet President George W. Bush in Washington on Monday. Thirteen members of one extended family were killed and the dead included seven children and four women, residents and the Palestinian Health Ministry said. Hamas's armed wing, decrying Washington's "political and financial support" for Israel, appeared to call on Muslims to attack U.S. targets, urging them "to teach the American enemy harsh lessons".