UNITED NATIONS: Osama Bin Laden's successor as the leader of Al Qaeda has struggled to unite its various factions, a UN report said Wednesday, but the group remains an evolving threat. The report, delivered to the UN Security Council by a group of experts, said Al Qaeda's Egyptian leader Ayman Al-Zawahiri had failed to rebuild the group's core leadership in Pakistan. But it said various groups affiliated with Al Qaeda are still adapting their tactics and seeking new targets, while retaining the ability to conduct deadly strikes. And, while the French-led military operation in Mali and an African Union campaign in Somalia have pushed back Al Qaeda militants, the Syrian civil war has seen hundreds of foreign volunteers join the cause there. "Al Qaeda and its affiliates are more diverse and differentiated than before, united only by a loose ideology and a commitment to terrorist violence," the report said. "A fragmented and weakened Al Qaeda has not been extinguished," it said, adding: "the reality of Al Qaeda's diminished capabilities and limited appeal does not mean that the threat of Al-Qaeda attacks has passed. "Individuals and cells associated with Al Qaeda and its affiliates continue to innovate with regard to targets, tactics and technology." The UN report tallies with claims made by US officials, including President Barack Obama, that so-called "core Al-Qaeda" has been weakened since Bin Laden's death in May 2011, while its regional wings continue to fight. But it also flies in the face of reports on Wednesday that a security alert declared for US missions in the Middle East was triggered when Zawahiri contacted Al Qaeda's regional commanders and ordered an attack.