UNITED NATIONS: UN leader Ban Ki-moon has no “hard”proof that al Qaeda was behind bomb attacks in Syria but is very concerned that terrorist groups are taking advantage of strife in the country, his spokesman said Friday.

Ban said on Thursday that he believed the group founded by the late Osama bin Laden carried out suicide bomb attacks in Damascus on May 10 which left at least 55 dead and nearly 400 wounded.

US and Russian officials have also said they believe al Qaeda has moved into the country where President Bashar al-Assad has been battling an uprising for 15 months.

“Do we have hard conclusive evidence at this point, no we don't,” UN spokesman Martin Nesirky told reporters when asked about Ban's statement.

But he added: “The Damascus attacks were clearly carried out by a group with organization and intent.Some of the attacks we have seen clearly bear some of the terrorist hallmarks with which we are familiar from elsewhere.”

Ban, UN-Arab League envoy Kofi Annan and Major General Robert Mood, the head of the UN ceasefire observer mission in Syria, share a “genuine concern”that “terrorist groups are already taking advantage of the continued violence and insecurity in Syria,” the spokesman said.

Annan has said he believes there is a “third element” operating in Syria alongside government and opposition forces.

“We have not yet been able to ascertain who this element belongs to -- who it is -- and we are in the process of doing so,” Annan's spokesman Ahmad Fawzi said in Geneva earlier.