BEIRUT, Lebanon -- Two major links with the outside world were shut down in Syria on Thursday, as Internet access disappeared across the country -- raising fears of an escalation of the government's crackdown on the uprising there -- and the largest commercial airport in the capital was closed because of fighting nearby, opponents of the Syrian government said.
Two companies that monitor Internet traffic, Arbor Networks and Akamai, released data suggesting that the disruption had continued for several hours after about 10 a.m. Syria time, and that there was no indication it had stopped. The Internet has been a strategic weapon for the rebels and the government alike, allowing activists to organize and communicate but also exposing them to surveillance.
Fighters, activists and ordinary citizens have uploaded video of rebel exploits and government crackdowns, but have also exposed rebel atrocities, making the Syrian war one of the most documented conflicts.
Reports differed over the reason for the airport closing. An antigovernment activist in Beirut said the airport in Damascus, the Syrian capital, was closed as rebel fighters edged closer, while the Syrian Observatory for Human Rights, an opposition group based in Britain, cited a fierce government offensive. The state news media reported that the airport was closed for maintenance, but the activist in Beirut said the shutdown was a result of "hit-and-run" strikes by rebels who were trying to force the closing of the site, a crucial conduit for supplies and money for the government. The shutdown, he said, robbed the government of a powerful symbol that the country was still operating normally.
The activist said the fighters did not necessarily have to hold the airport to prevent it from operating. "If you can't use it, what is the point?" said the activist, who added that he had been in contact with fighters in that area who had been gradually working their way toward the airport.
Other activists also reported the closing of the Damascus airport, and several airlines said they had halted flights. An official at EgyptAir said it had indefinitely suspended flights to Damascus because of the security situation, although morning flights to the northern city of Aleppo were operating.
Syria's information minister, Omran al-Zoubi, was quoted on a Lebanese news Web site as denying reports that the airport road was closed, and he declared that the government was not responsible for the Internet disruption. The state news media issued no immediate reports of fighting at the airport, according to the Twitter feed for SANA, the official Syrian news agency.
But fighting has been especially intense around Damascus over the past two weeks, with rebels seizing many air bases and weapons, attacking in a string of eastern suburbs and approaching the airport to the southeast. On Sunday, rebels reported seizing three military installations in the area, including an air base known as Marj al-Sultan, and they have reported overrunning several other air bases since then.
Rebels have also put the government under increasing pressure in recent weeks by taking oil fields in eastern Syria and a major air base near Aleppo, and demonstrating their growing ability to shoot down aircraft.
Some analysts have speculated that if the government believed that core interests were threatened -- for example, if Aleppo was in danger of being cut off from Damascus, or if the rebels surrounded the capital -- the military might unleash a desperate crackdown.
"Deliberately or not, the rebels could be forcing the regime's hand," said Yezid Sayigh, a military analyst at the Carnegie Middle East Center in Beirut.
The Internet cutoff apparently made some activists suspect that the moment was at hand.
Antigovernment activists warned that the Syrian authorities might be planning to escalate their response against the uprising after Internet access was closed. Activists said only residents with satellite equipment could access the Web.
A technology company called Renesys reported a "major outage" on its blog and said that all of the country's 84 IP address blocks were unreachable, "effectively removing the country from the Internet." The Local Coordinating Committees, a coalition of activist groups, reported that the Internet disruption had affected most parts of Damascus and its suburbs, as well as most parts of the governorates of Hama, Homs and Dara'a. Access in the governorates of Tartous and Swaida, and in some parts of Deir al-Zour and Raqqa, was also affected, the group said.
Throughout the uprising of about 20 months, the Internet has been used to document and highlight civilian casualties that have now reached about 40,000, in addition to highlighting rebel claims of territorial gains and weapons seizures. With physical access to the country severely limited, it has been difficult to evaluate the veracity and context of such documentation. The government's supporters also clash with its opponents over social networks like Twitter.
Kareem Fahim and Mai Ayyd contributed reporting from Cairo, and Christine Hauser from New York.
This article originally appeared in The New York Times.