Two US-based internet-monitoring companies say Syria has shut off the internet nationwide.
A blog post on Renesys, a US company which tracks internet traffic worldwide, said that at 12.26pm in Damascus, Syria's international internet connectivity shut down completely.
Akamai Technologies also confirmed a complete outage.
The Syrian government has previously cut phone lines and internet access in areas where regime forces were conducting major military operations.
An activist near Damascus who gave his name as Abu Sham said the government had cut the internet in the southern neighbourhoods of the capital on Thursday.
Another activist, Abu Qais al-Shami, who lives outside the country, also said land-lines, mobile phone signals and the internet were cut in several of the capital's southern neighbourhoods, including Yarmouk and Tadamon, around noon.
He said he had been able to communicate with contacts in Syria by using satellite telephones.
Elsewhere in the capital, warplanes bombed Kafr Souseh and Daraya, two neighbourhoods that fringe the centre of the city where rebels have managed to hide out and ambush army units, opposition activists said.
The past two weeks have seen military gains by rebels who have stormed and taken army bases across Syria, exposing Assad's loss of control in northern and eastern regions despite the devastating air power he has used to bombard opposition strongholds.
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