ABANDONED by the West and under siege from one of the best-equipped armies in the Middle East, Free Syrian Army rebels fighting in Aleppo are contending with a new threat – an influx of foreign jihadist fighters aiming to hijack the revolution for their own ends.

The accounts by two Western journalists released from captivity in a jihadist camp in northern Syria last week tally with numerous other sources in the area, describing a new wave of young jihadists, including British men with London and Birmingham accents, crossing the Turkish border to fight the regime in Syria, often at odds with indigenous Syrian rebels.

British photographer John Cantlie and a Dutch national, Jeroen Oerlemans, were freed last Thursday in an FSA rescue raid after being threatened with execution during their detention by a group of up to 100 young jihadists from North Africa, Britain and the Caucasus. “I don’t think they were al-Qa’ida, they seemed too amateurish for that,” Mr Oerlemans said after his release. “They said, ‘We are not al-Qa’ida, but al-Qa’ida is down the road’.”

So far, the influence of foreign Sunni militants on the Syrian revolution has been limited, despite the efforts of the regime to magnify the threat they pose. Few Syrian rebels are fighting to replace the rule of Bashar al-Assad with an Islamic state under sharia law. The presence of foreign radicals and al-Qa’ida affiliates is regarded as a threat to the FSA’s greatest hope – intervention by the West on their behalf.

One sign of foreign presence came in April when the leader of the al-Qa’ida-linked Lebanese group Fatah al-Islam accidentally blew himself up near the town of al-Qusayr in southern Syria. Abdel Ghani Jawhar was leading a group of 30 travelling as “mujaheddin”, holy warriors, rather than under the name of the banned terror group.

“It is normal to fight from country to country,” said a Syrian activist based in al-Qusayr, contacted on Skype. “But we are refusing to allow them to organise themselves – Salafists, Muslim Brotherhood, al-Qa’ida – but if individuals come, no problem.”

The rising numbers of foreign fighters in Syria comes at a moment of renewed sectarian tension in Iraq, where an invigorated al-Qa’ida presence was blamed for a wave of attacks that killed more than 100 people last week. Any nexus between militants in the two countries could prove a major source of regional instability in a post-Assad era, expanding tensions between Sunni and Shia communities.

The relationship between al-Qa’ida in Iraq and Syria is already long-established. In Syria, the movement is represented by the al-Nusra Front for the People of the Levant, which has claimed responsibility for at least four of the suicide bomb attacks this year.

Noman Benotman, senior analyst at the counter-extremism think tank Quilliam, said that al-Nusra was typical of al-Qa’ida’s rebranding. “Al-Qa’ida’s goal right now is not necessarily to fight in a high-profile way, but to re-establish its strategic influence in the region, through groups with new names, such as Ansar al-Sharia in Libya and al-Nusra in Syria,” he said.