Renesys, monitoring the situation, said that "Syria's international Internet connectivity shut down. In the global routing table, all 84 of Syria's IP address blocks have become unreachable, effectively removing the country from the Internet," and traceroutes into Syria were failing, which ultimately is expected in a major outage."
Google's Transparency Report has also confirmed the outage, although as a tweet I received suggested, some archaic dial-up connections are possibly still active.
Reports state that a "pro-government" television station broadcast the message that "terrorists" caused the countrywide Internet outage, and the state were not involved. The message said:
"It is not true that the state cut the Internet. The terrorists targeted the Internet lines, resulting in some regions being cut off."
The main communications and Internet cable was cut -- and engineers were working to repair the fault, according to Syria's telecommunications minister. However, an investigated conducted by CloudFlare reinforces the idea that this simply may not be true.
The team mention several reasons why one singular cable-cutting exercise couldn't take down the entire system. Most importantly, all connectivity was severed in Syria, and not merely some regions. In addition, Internet access is provided by state-run firm Syrian Telecommunications Establishment, who provides the main "Autonomous System" (AS) gateway to the Internet.
When connections were severed, each Border Gateway Protocol (BGP) was withdrawn from the system, which prevented Syrian IP spaces from connecting -- achievable only when the BGP provider, the AS system, modifies communications routes. The video below documents routes being cut off within the space of two minutes:
CloudFlare's investigation suggests that Syria may have a number of "edge routers", controlled by Syrian Telecommunications, that were able to systematically remove every communications channel through router software updates, rather than physical technology failures or aforementioned cable-cutting "terrorist" activities.
Finally, Syria does not simply have one cable. Four -- including three undersea cables -- keep Syria connected, and for the Syrian telecommunications minister's statement to be true, each one would have had to be cut simultaneously.