US Senator John McCain paid a surprise visit to Syria on Monday and met with rebels in the war-torn country, the Voice of America reported. McCain's spokesman Brian Rogers said the senator crossed from Turkey into Syria with Free Syrian Army rebel commander General Salam Idris on Monday, and remained for several hours before returning to Turkish territory. The spokesman did not spell further details about McCain's visit. McCain is one of the leading voices in the US Congress calling for greater US assistance to the rebels. His brief visit to Syria makes him one of the most senior US officials to enter the country since the anti-Assad rebellion evolved into a civil war after peaceful protests in March 2011