REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE CONTENT OF THIS VIDEO, WHICH HAS BEEN OBTAINED FROM A SOCIAL MEDIA WEBSITE.<br /> <br />An aid convoy comes under fire in the besieged Syrian city of Homs.<br /> <br />It happened late Saturday when mortar fire and gunshots hit the convoy of at least nine trucks.<br /> <br />They were from the United Nations and the Syrian Arab Red Crescent, on their way to a rebel held district to deliver food and medicine to civilians trapped in the fighting for months.<br /> <br />Reuters can't independently verify this video, which was posted online and purports to be the aftermath of the attack.<br /> <br />It's unclear who launched the attack.<br /> <br />Both sides blame the other.<br /> <br />Syrian TV said at least four aid workers were wounded.<br /> <br />The attack violates a three-day ceasefire designed to get much-needed food and supplies inside Homs.<br /> <br />It also threatens to unravel a humanitarian deal that included the evacuation of civilians.<br /> <br />The deal had been the first concrete
