The Internet blackout, confirmed by two U.S-based companies that monitor online connectivity, is unprecedented in Syria's 20-month-old uprising against President Bashar Assad. Regime forces have suffered a string of tactical defeats in recent weeks - losing air bases and other strategic facilities - and the blackout may be an attempt by the government dull any further rebel offensives by hampering communications.
Authorities often cut phone lines and Internet access in select areas where regime forces are conducting major military operations to disrupt rebel communications. Activists in Syria reached Thursday by satellite telephone confirmed the blackout.
Renesys, a U.S.-based network security firm that studies Internet disruptions, said in a statement that Syria effectively disappeared from the Internet at 12:26 p.m. local time.
"In the global routing table, all 84 of Syria's IP address blocks have become unreachable, effectively removing the country from the Internet," Renesys said.
Akamai Technologies Inc., another U.S-based company that distributes content on the Internet, also confirmed a complete outage for Syria.
With pressure building against the regime on several fronts, rebels have been trying to push their way back into the capital after being largely driven out after a July offensive into Damascus. Opposition fighters were battling government troops near the city's international airport Thursday, the Britain-based Syrian Observatory for Human Rights said, prompting the military to close the road to the facility.
Both the Dubai-based airline Emirates and EgyptAir have temporarily suspended flights to Damascus.
A senior EgyptAir official said the flight to Damascus scheduled for Friday has been canceled in light of the deteriorating conditions at Damascus airport. The official said an emergency meeting is scheduled to look into whether to halt all flights to the Syrian capital.
The airport lies on the capital's southern outskirts, and the surrounding districts have been strongholds of support for the rebels since the start of the uprising.
Government warplanes struck the rebellious districts around Damascus on Thursday, including Daraya, where fighting has raged for days, as rebels fight their way into the capital, the Observatory said.
The revolt in Syria began with peaceful protests but turned into a civil war after the government waged a brutal crackdown on dissent. Activists say more than 40,000 people have been killed.
In the country's south, rebels bombed the house of a top member of the country's ruling Baath party Thursday, killing him and his three body guards, activists said.
The bombing took place in Daraa, where the uprising began in March 2011. Since then, rebels have frequently targeted regime figures and military commanders. The increasing frequency of bombings, a hallmark of Islamic extremists like al-Qaida, has led to concerns about the growing role of Islamist militants in the civil war.