Phone and internet networks were down across most of Syria for a second straight day, amid reports of fighting near the capital’s international airport.
The length of internet blackout, which continued on Friday, is unprecedented in Syria's 20-month-old uprising against President Bashar al-Assad.
Renesys, US-based company that monitor online connectivity confirmed that "all 84 of Syria's IP address blocks had become unreachable [on Thursday], effectively removing the country from the Internet".
Residents in some areas reported on Friday that they could access the internet but "with great difficulty".
"It is also very difficult to reach people by phone. But we have received reports that it is possible to communicate between certain regions via fixed telephone lines," Rami Abdel Rahman, the head of the Syrian Observatory for Human Rights, reported.
AFP news agency correspondents noted that internet and telephone communications, including mobile phones, were cut in the capital.
The official news agency SANA had still not resumed transmission on Friday after its feed was cut on Thursday at midday. Its website was also inaccessible.
Syrian state TV denied the blackout was nationwide. It said the outage was caused by a technical failure, only affected some provinces, and that technicians were trying to fix the problem.
Syria's minister of information said "terrorists", not the state, were responsible for the outage, a pro-government TV station reported. Internet companies said that this was unlikely.
The US on Thursday accused the Syrian regime of cutting off internet and telecommunications links in the war-torn country, branding the move a sign of desperation.
Amnesty International said on Twitter that reports of an internet shutdown were "very disturbing".
The government has previously cut phone lines and internet access in areas where regime forces are about to conduct major military operations.
Suspension of flights
Meanwhile, fierce fighting was reported on the 27-kilometre road linking Damascus to the airport.
"After strong clashes, rebels were able to take control of a part of the airport road between the second and fourth bridge," activists said.
State television had on Thursday night quoted the information ministry as saying that the Damascus airport road, closed for much of the day due to the fighting, had been "secured" after military intervention.
In-depth coverage of escalating violence across Syria
Both EgyptAir and Emirates had on Thursday announced suspension of flights due to the fighting.
A Syrian security source said: "[On Thursday], we sent a telegram to the foreign companies still working in Syria and SyrianAir [the national carrier] to inform them of the status of the road to the airport so they would cancel their flights to Damascus."
"Today after the road was secured, we sent a new telegram to inform them that security was restored," she told AFP.
A military source in Damascus said that the army had taken control of the western side of the road leading to the airport and a small portion on the east by dawn, allowing travellers to move through.
"But the most difficult part is yet to come. The army wants to take control of the eastern side, where there are thousands of terrorists and this will take several days," he said, using the term regime officials use to describe rebel fighters.