The Syrian government has shut down the Internet across the country and cut cellphone services in select areas as rebels and government troops waged fierce battles near the capital's airport, wounding two Austrian peacekeepers and forcing international airlines to suspend flights, activists said.

The blackout, confirmed Thursday by two U.S-based companies that monitor online connectivity, is unprecedented in Syria's 20-month-old uprising against President Bashar al-Assad.

Regime forces have suffered a string of tactical defeats in recent weeks, losing air bases and other strategic facilities, and pulling the plug on the Internet may be an attempt by the government to dull any additional rebel offensives by hampering communications.

Syrian state TV denied the blackout was nationwide. It said the outage was cause by a technical failure, only affected some provinces and that technicians were trying to fix the problem.

Syria disappears from the Internet

Authorities often cut phone lines and Internet access in select areas where regime forces are conducting major military operations to disrupt rebel communications. Activists in Syria reached Thursday by satellite telephone confirmed the blackout.

Renesys, a U.S.-based network security firm that studies Internet disruptions, said in a statement that Syria effectively disappeared from the Internet at 12:26 p.m. local time.

"In the global routing table, all 84 of Syria's IP address blocks have become unreachable, effectively removing the country from the Internet," Renesys said.

It added that the main autonomous system responsible for Internet in the country is the Syrian Telecommunications Establishment, and that "all of their customer networks are currently unreachable."

Akamai Technologies Inc., another U.S-based company that distributes content on the Internet, also confirmed a complete outage for Syria.

Fighting rages in Damascus

With pressure building against the regime on several fronts, and government forces on their heels in the key fight over the northern commercial hub of Aleppo, rebels have been trying to push their way back into Damscus after largely being driven out after a July offensive.

On Thursday, opposition fighters were battling government troops near the city's international airport, the Britain-based Syrian Observatory for Human Rights said, forcing the military to shut the road to the airport.

The Syrian Information Ministry said later that the airport road was secure after attacks by "terrorist groups" on motorists, according to state TV. It was not immediately clear whether the road had been reopened.

Austria Press Agency said two Austrian soldiers assigned to the United Nations Disengagement Observer Force in the Golan Heights were wounded Thursday afternoon after their convoy came under fire on the way to the airport. The report, quoting the Defense Ministry spokeswoman, said the two did not appear to be critically wounded.

Rami Abdul-Rahman, the head of the Observatory, said the regime has started a major offensive around the airport on the southern edge of Damascus where rebels have been particularly active in recent weeks.

Abdul-Rahman, who relies on a network of activists throughout Syria, said large convoys of government reinforcements were seen on the airport road heading south in the direction of the airport, 25 kilometres southeast of Damascus.

He said the fighting on Thursday was concentrated in and around the villages of Beit Saham and Aqraba near the airport. State-run Syrian TV said government forces were chasing "al-Qaeda elements" around the capital, mostly in the eastern suburbs of Douma and the southern suburb of Daraya.

Rebels make advances

The operation around the capital comes days after rebels made significant advances around Assad's seat of power.

Last week, they captured a major helicopter base just outside the capital, and rebels and activists recently said a major opposition offensive on Damascus was in the works.

Despite months of sporadic fighting and crumbling security in Damascus, the city's airport has remained open. But the fighting Thursday prompted both the Dubai-based airline Emirates and EgyptAir to temporarily suspend flights to Damascus.

senior EgyptAir official said the flight to Damascus scheduled for Friday has been canceled and that the airline has scheduled an emergency meeting to look into whether to halt all flights to the Syrian capital.

The airport lies on Damascus' southern outskirts, and the surrounding districts have been strongholds of support for the rebels since the start of the uprising.

Government warplanes struck the rebellious districts around Damascus on Thursday, including Daraya, where fighting has raged for days, the Observatory said.

The revolt in Syria began with peaceful protests but turned into a civil war after the government waged a brutal crackdown on dissent. Activists say more than 40,000 people have been killed.