Ayman al-Zawahiri, Al Qaeda’s second-in-command, gained support from a linked militant group In Iraq and swore more attacks in vengeance for Osama bin Laden’s death.

The caliph of the Islamic State of Iraq (ISI), Abu Baker al-Baghdadi al-Husseini al-Qurashi, grieved over bin Laden's death. In an Islamist website he said, "I tell our brothers in al Qaeda organization and on the top of them Sheikh Mujahid Ayman al-Zawahiri ... be merry, you have faithful men in the Islamic State of Iraq who are following the right path and will not quit or be forced out."

"I swear by God, blood for blood and destruction for destruction," the caliph added which is a clear indication of retribution.

Zawahiri, who is expected to succedd bin Laden, appears to be an Egyptian-born doctor. He met bin Laden in the mid-1980s when both were in Pakistan to assist rebels fighting the Soviets in Afghanistan. Zawahiri’s present location is unknown.

In a separate statement, ISI claimed responsibility of an assault which transpired at a police building in the Shi'ite city of Hilla that claimed lives of 20 people.

ISI is believed by intelligence analysts to have been established by the al Qaeda in Iraq as a local umbrella group for rebellious associations.

Security officials have earlier declared that bin Laden's death would only make a little practical impact on al Qaeda group in Iraq. It may be a weak one but still a deadly Islamist uprising that could launch strikes for the next decade.

Al Qaeda in Iraq may seek instantaneous revenge for the killing of the world's most wanted man but is seen to be more of a problem to the Iraqi government than a destabilizing force in the long run, security officials accounted.