Ban Ki Moon has said he believes that Al Qaeda was behind last week's bomb attacks in the Syrian capital, Damascus.
At least 55 people were killed and another 372 injured when two car bombs exploded in the south of the city on May 10. State media blamed "terrorists," but opponents of President Bashar al-Assad claimed that the government could have orchestrated the attacks.
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Speaking in New York today, the UN Secretary General said he believed the bombings were the work of Islamist extremists.
"Very alarmingly and surprisingly, a few days ago, there was a huge serious massive terrorist attack," Agence France Presse cited Ban as saying.
"I believe that there must be Al Qaeda behind it. This has created again very serious problems."
The Syrian government has long blamed the unrest on foreign terrorists.
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Earlier this month, Al Jazeera reported, Damascus sent the UN a list of 26 foreign nationals who had been detained after allegedly entering Syria to fight, 20 of whom were described as members of Al Qaeda.
US Defense Secretary Leon Panetta said last week that US intelligence indicated "an Al Qaeda presence in Syria," but said the extent of its activity was unclear.
GlobalPost's correspondents in the region say that Assad's regime has a history of manipulating jihadi groups to serve its own political interests.
Ban said today that the UN was making its "best efforts to protect the civilian population" in Syria, but that so far the presence of international monitors had had only a "dampening effect" on the violence.
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