BEIRUT, Lebanon — Syria lost two major links with the outside world on Thursday as the largest commercial airport in the capital canceled flights because of fighting nearby and Internet access disappeared across the country, perhaps signaling an impending escalation by the government against the uprising, opponents of the Syrian government said.

The disruption of the airport, Damascus International — a crucial conduit for supplies, money and weapons for the government — was a measure of how intense the conflict has become around the capital in recent weeks. As security forces launched a major counteroffensive against rebels nearby, the government’s willingness to carry out military operations in the area suggested that it was feeling the pressure of rebel advances.

Keeping the airport open has helped the government project a sense of normalcy, and interrupting service creates problems, activists said, because the large planes needed for supplies cannot land at smaller military airports.

At the same time, two companies that monitor Internet traffic, Arbor Networks and Akamai, released data demonstrating that the Internet went out across the country around 10 a.m., and there was no indication by the evening that it had returned.