"One of the most dispersed type of assault rifles in the world is the Belgian manufactured FN FAL which dates back to the 1960s. It's probably quite likely to be old. They have a far greater range than the Kalashnikov-pattern weapons circulating in the region," said Conflict Armament Research's Bevan.
Two maritime security sources said they were aware of attempts also being made to procure light arms on behalf of Syrian rebels via private security firms in South Africa.
"What's being discussed are test runs using surplus arms inside South Africa. We are talking about paper bags full of cash involved. It's as simple and crude as that and it's untraceable," the maritime intelligence source said.
However, one South African defense contractor said the government kept a very close eye on munitions exporters.
"It's quite normal for South African citizens to be proposing or organizing contracts in the Middle East, but the government would not let arms go either directly or indirectly to a rebel movement," the contractor said. "No company is going to take the risk because they are going to lose so much."
A foreign ministry spokesman declined to comment.
U.S. and allied national security officials say they remain dismayed at the rebels' inability to form a coherent national movement and continue to be dogged by factional rivalries. The U.S. and its allies also fear a growing presence among the rebels of Islamic militants, some of whom Western intelligence officials say may be affiliated with al Qaeda in Iraq.
Nick Pratt, who helped arm and train anti-Soviet guerrillas in Afghanistan for the CIA in the 1980s, said foreign suppliers of an insurgency had to tread cautiously.
"There has to be face to face contact in the field with the people who are going to use these things, to give you some reassurance that the weapons are getting into the right hands," said Pratt, a retired U.S. Marine Corps colonel.
"What you don't want to do is go through a third party that takes control of the distribution for you. You may find the supplies end up in places, and with people, you don't want."
For the moment, it appears unlikely that either the U.S. or many if any of its allies in Europe are gearing up for a major push to greatly accelerate arms deliveries to Syrian rebels. Nothing on the lines of the support given to rebels in Libya last year is in anywhere in sight.
Graham Cundy, a former UK military officer with experience of special operations, told Reuters: "In situations like Syria, UK government priorities are far more about intelligence gathering and understanding what is going on, than in supplying one group or another. The tribal and communal mix is far more complicated than in Libya."
"Any intelligence service worth its salt will be hanging around the border areas and getting to know the networks that are supplying the players," said Cundy, who has counter-terrorism experience in the Middle East as well as other areas.
"They will be monitoring who gets what, because the same networks that supply opposition groups may well be the same networks that supply extremists. You don't want a SAM-7 missile ending up in the hands of a determined organization with links back to communities in the UK, " he said.
Iraq said last week it had "solid information" that al Qaeda militants were crossing from Iraq into Syria to carry out attacks in the 16-month-old insurgency.
Western officials say anti-Assad rebels as well as forces marshaled by or supporting the Syrian government have killed civilians, although on balance more atrocities are attributed to the government side. Opposition sources said about 220 Syrians, mostly civilians, were killed in a village in the rebellious Hama region this week, largely by army artillery bombardment
Assad, whose family has ruled Syria for 42 years, has accused Qatar, Saudi Arabia, Turkey and the U.S. of funding "terrorists". Last week a group of Western and Arab states from the "Friends of Syria" agreed to "massively increase" aid to Syrian rebels and provide them with communications equipment.
"Although the intensity of the conflict is likely to increase over the coming weeks and months - especially as anti-regime forces become better armed - there is little to suggest that either side will be able to gain a decisive victory through the use of force alone in the short term," said Torbjorn Soltvedt, senior analyst with risk analysis firm Maplecroft.
(Additional reporting by William Maclean and Mark Hosenball in London, Jonathon Burch in Ankara, Jon Herskovitz and Ed Cropley in Johannesburg, Susan Cornwell in Washington, Tsvetelia Tsolova in Sofia, Ioana Patran in Bucharest and Pavel Polityuk in Kiev, writing by Jonathan Saul; editing by Ralph Boulton)