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.