An al-Qaida front group in Iraq has confirmed the killing of its two top leaders but vowed in a statement that its members were not cowed by their death and would continue to fight."After a long journey filled with sacrifices and fighting falsehood and its representatives, two knights have dismounted to join the group of martyrs," the statement said. "We announce that the Muslim nation has lost two of the leaders of jihad, and two of its men, who are only known as heroes on the path of jihad."Maliki reacts to al-Qaida violenceTheir deaths were triumphantly announced last Monday by Iraqi Prime Minister Nouri al-Maliki. US Vice President Joe Biden called the killings a "potentially devastating blow" to al-Qaida in Iraq.But four days later, officials believe al-Qaida struck back, bombing mosques, shops and the office of an influential Shiite cleric to kill 72 in Iraq's bloodiest day of the year so far. Homes of police also were bombed. Al-Maliki said the insurgents were fighting back after the deaths of their two leaders.Maliki has seized on the militants' killings to show he can restore stability to Iraq after years of bloodshed. Following his political coalition's second-place finish in the March 7 parliamentary elections, Maliki is locked in a tight contest with secular challenger Ayad Allawi to see who will form the next government.The four-page statement by the Islamic State of Iraq was posted on a militant website early Sunday. It concluded: "The war is still ongoing, and the favorable outcome will be for the pious."The statement comes a week after Iraqi and US security forces raided a safe house near Tikrit, Saddam Hussein's hometown north of Baghdad, killing Abu Omar al-Baghdadi and Abu Ayyub al-Masri.The Islamic State of Iraq is an offshoot of al-Qaida in Iraq. Baghdadi was its self-described leader and was so elusive that at times US officials questioned whether he was a real person or merely a composite of a terrorist to give an Iraqi face to an organization led primarily by foreigners.Masri, a weapons expert who was trained in al-Qaida camps in Afghanistan in the late 1990s, was the shadowy national leader of al-Qaida in Iraq.