Syrian rebels are believed to have used captured surface-to-air missiles to shoot down a helicopter and a fighter-bomber of the embattled Damascus regime in what could be an important tactical gain in the country's 20-month-old civil war.

If the 1979-89 Afghanistan War between Islamist fighters and the Soviet army is anything to go by, when U.S.-supplied Stinger missiles turned the tide against Soviet air power, the Syrian rebels' acquisition of such weapons could be a potential game-changer.

The possible deployment of NATO Patriot air-defense missiles to Turkey to protect the alliance member against possible chemical missile attacks by its southern neighbor, could add considerable firepower against the Syrian regime's hitherto unchallenged control of the skies at a critical juncture.

The regime's been increasingly using air power to counter rebel offensives in which the insurgents have won control of large areas of the north and east and in outlying areas of Damascus.

Last week, northern rebels downed a fighter-bomber outside Darat Azzah near Aleppo, Syria's second city and commercial heart where anti-government forces hold large areas. The wounded pilot was captured.

At about the same time, a Soviet-built Mil Mi-8 transport, apparently being used to attack rebel positions around Aleppo, was brought down. Several grainy videos uploaded onto the Internet showed a SAM hitting the helicopter before it crashed.

The rebels claim they looted the shoulder-fired SAMs from military bases they've overrun during the last few weeks. At least four major installations, two of them in the north, are reported to have been captured.

The regime hasn't admitted losing these or any aircraft to rebel fire. But it was just a matter of time before the rebels acquired an air-defense capability against the regime's air power that has increasingly been turned upon them in recent weeks.

Aerial attacks on rebel-held sectors of major cities like Damascus and Aleppo suggest a growing desperation by President Bashar al-Assad and his inner circle as the rebels gain -- and more importantly, hold -- ground.

The rebels have been clamoring for surface-to-air missiles for months.

The Americans and the European Union have been reluctant to provide them, fearing they might fall into the hands of jihadist groups and be used against airliners.

But that policy could change if recent rebel attempts to unify their ranks and establish a recognizable military chain of command prove to be effective against the regime led by minority Alawites, an offshoot of Shiite Islam.

However, Saudi Arabia and Qatar, Assad's key Arab foes and Sunni-dominated monarchies, have been funding arms shipment to the mainly Sunni rebels, although it's not clear whether these included SAMs.

Qatar is understood to have supplied heavy machine guns bought in Libya, still awash with weaponry from the country's 2011 civil war.

"Saudi Arabia and Qatar have been chafing ever more loudly against the U.S. veto on supplies of sophisticated, potentially decisive weapons such as shoulder-launched anti-aircraft missiles ...to the rebels," observed British analyst Julian Borger.

A rebel commander in Idlib province, a major battlefront in the north, claimed in October he'd received a small number of Soviet heat-seeking weapons, dating from the mid-1970s, from Qatar via Turkey. But that would seem to be the exception.

It is known that that the weapons captured by the rebels include the heat-seeking 9K32 Strela, NATO Codename SA-7 Grail, the first Soviet shoulder-fired SAM to enter service in 1968 and which has been used in virtually every conflict since.

On Nov. 29, The Washington Post quoted Middle Eastern intelligence officials as saying rebels had acquired as many as 40 shoulder-fired SAMS in recent weeks and are using them with growing effectiveness.

The SA-7 is an outmoded system and such weapons may no longer be reliable in combat. Most modern military aircraft have electronic countermeasures that make the Strelas less effective.

Borger reported that videos and eyewitness accounts "suggest the rebels have also seized a later version, the SA-16. They have also shown off training versions of a state-of-the-art Russian-made SA-24."

If the Syrian rebels do have, or could soon get, such weapons, "that would be the first time we've seen the SA-24 in the hands of a non-state actor," says Matt Schroeder of the Federation of American Scientists.