Syrian rebels battled regime troops south of the capital Friday and internet and telephone lines were cut for a second day, but the government reopened the road to the airport in Damascus in a sign that the fighting could be calming, activists said.

The general manager of the Syrian Civil Aviation Agency, Ghaidaa Abdul-Latif, said the airport was operating "as usual" on Friday. One day earlier, international flights were cancelled because of the violence.

President Bashar al-Assad's regime and opposition activists blamed each other for the communication blackout, which is the first to hit the whole country since Syria's 20-month-old uprising began.

Technology experts say it's unlikely that the rebels are capable of the effort because it would involve severing three undersea internet cables and another that runs above ground through Turkey.

Following through on prior threats against the Syrian regime, web hacking group Anonymous took down the Industrial Bank of Syria's website and posted a message on the page asking the Assad government to work for peace.

Syrian authorities previously have cut internet and telephones in areas ahead of military operations. On Friday, some land lines were working sporadically.

Fighting south of Damascus

The Britain-based Syrian Observatory for Human Rights said the main road to the airport reopened early Friday afternoon. There were intense clashes after midnight in villages and towns near the airport but the area was calm by the late morning, the group said. It said rebels were able to destroy several army vehicles near the airport.

The Observatory, which has a network of activists around Syria, reported fighting in southern neighbourhoods of Damascus including Qaboun and Hajar Aswad. The group said it was able to contact its sources who used satellite telephones.

Activists say Assad's regime pulled the plug on the internet on Thursday, perhaps in preparation for a major offensive. Cellphone service also went out in Damascus and parts of central Syria, they said.

Thursday's violence appeared to be focused on southern suburbs near the airport, forcing the military to shut the road to the facility. The surrounding districts have been strongholds of rebel support since the uprising began.

Internet outage unprecedented

Thursday's violence appeared to be focused on southern suburbs near the airport, forcing the military to shut the road to the facility. The surrounding districts have been strongholds of rebel support since the uprising began.

With pressure building against the regime on several fronts and government forces on their heels in the battle for the northern commercial hub of Aleppo, rebels recently began pushing back into Damascus after largely being driven out of the capital following a July offensive.

A Syrian boy reads a torn paper inside his destroyed school classroom, in Aleppo, Syria, on Thursday. (Associated Press)

One Damascus resident reported seeing rebel forces near a suburb of the city previously deemed to be safe from fighting.

The internet outage, confirmed by two U.S.-based companies that monitor online connectivity, is unprecedented in Syria's uprising against Assad, which activists say has killed more than 40,000 people since the revolt began in March 2011.

Regime forces have suffered a string of tactical defeats in recent weeks, losing air bases and other strategic facilities. The government may be trying to blunt additional rebel offensives by hampering communications.

U.S. State Department spokeswoman Victoria Nuland on Thursday condemned what she called the regime's "assault" on Syrians' ability to communicate with each other and express themselves. She said the move spoke to a desperate attempt by Assad to cling to power.

With files from CBC News