Well-armed Free Syrian Army fighters on the frontline in Damascus, and above, in Deir alZor in the east of Syria. Weaponry is getting to them via Esenboga Airport in Turkey

end up among the ranks of al-Nusra and their jihadist allies?

In its detailed investigation the NYT quoted two rebel commanders, Hassan Aboud of Soquor al-Sham and Abu Ayman of Ahrar al-Sham, both “moderate” Islamist groups who claim that whoever is vetting the weapons supplies is not doing a very good job.

“There are fake Free Syrian Army brigades claiming to be revolutionaries, and when they get the weapons they sell them in trade,” Aboud was quoted as saying in the NTY investigation.

LAST month, t he Leicester-based blogger Eliot Higgins ( aka Brown Moses) blew the lid on the covert international operation to arm the Syrian opposition by discovering that a batch of Croatian weapons made their way into in the hands of Syrian rebels. He also found that Saudi- purchased weapons were turning up in the hands of jihadists all over the country.

Higgins’s work on analysing Syrian weapons, which began as a hobby, is now regularly used by human rights groups and has led to questions in the UK Parliament.

Largely unpaid and working from a laptop more than 3000 miles away from Damascus, Higgins has been accused by conspiracy theorists of being in the pay of everyone from the CIA and MI6 to the Israeli intelligence service Mossad.

However, according to Peter Bouckaert, emergencies director at Human Rights Watch, who worked with Higgins to document the use of cluster bombs in Syria: “Brown Moses is among the best out there when it comes to weapons monitoring in Syria.”

His work is testimony to the power of a new breed of online investigator tackling work that was once the exclusive preserve of intelligence and military specialists.

Among Higgins’s revelations over arm supplies in Syria was exposing for the first time the extensive use of cluster bombs despite the Syrian government’s denial that they existed inside the country. He also exposed the proliferation of shoulder-launched heat-seeking missiles known as Manpads, and their most recent use in the hands of rebels fighting around Aleppo. Perhaps most significant, however, was his discovery of a cache of weapons from Croatia in the hands of rebel groups fighting in the southern Syrian province of Deraa. Subsequent reports alleged the weapons were financed by Saudi Arabia with the knowledge of the US and CIA.

For now, many of the countries at the centre of the arms supply chain, including Croatia and Jordan, have denied any role in moving arms to the Syrian rebels, but the evidence is mounting.

As the rivalry between rebel groups intensifies in tandem with their own front-line efforts directed at ousting the Assad regime, there are growing fears that the Islamists’ gains in Syria’s north-eastern provinces could split the country along a north-south, Aleppo-Damascus divide – not unlike the intense rivalry in Libya between the Islamist east, centred on Benghazi, and the west, dominated by Tripoli.

On Friday t he UN Security Council began informal talks on imposing sanctions on the al-Nusra Front after it pledged allegiance to al-Qaeda leader Ayman al-Zawahri.

French foreign ministry spokesman Philippe Lalliot said given Wednesday’s announcement by al-Nusra chief Abu Mohammad alGolani, it was logical to look at how to deal with the Syrian group in the framework of the “fight against terrorism”.

“One option is to act at the UN Security Council ... through the alQaeda 1267 sanctions committee,” he said.

He added: “It is one solution that we are studying and discussing informally with our UN Security Council partners and European allies.” Sanctions could include assets being frozen and travel bans.

At the very least, last week’s announcement by the al- Nusra Front, alongside other developments, undoubtedly confirms suspicions that the Syrian civil war is creating opportunities for international jihadists to coalesce in the region.

While the problem facing the UN will be how best to sanction these now confirmed al-Qaeda allies, the challenge facing Washington and those other sponsors of the arms supplies reaching Syrian rebels will be how best to keep such weaponry out of the jihadists’ hands. Such a task seems near-impossible amidst the myriad groups that now make up the country’s armed opposition.

Difficult as it is to believe, Syria’s civil war looks set to get dirtier than ever.