Sunni jihadist groups in northern Syria have secured a large supply of the type of anti-aircraft missiles that the Obama administration has urgently tried to keep away from rebel groups fighting the civil war, video footage shows.

The missiles, believed to be shoulder- launched SA-16s, are displayed in a video allegedly made by a Chechen-dominated jihadist group of foreign fighters. They are known to pose a potent risk to most types of aircraft and have been urgently sought by all rebel groups as a means of breaking the dominance over Syrian skies enjoyed by President Bashar al-Assad's air force.

The English speaker on the jihadist video, who calls himself Abu Musab, does not specify where the missiles came from, but it is believed they may have been seized during a raid on the Brigade 80 military base, on the outskirts of Aleppo airport, in February.

Separate reports suggest some opposition groups may have found an alternative supply line from outside Syria. However, while some light weapons are allowed into Syria, the CIA has led intensive efforts to ensure anti-aircraft missiles, such as the SA-16s, are not allowed across the Turkish or Jordanian borders.

The video emerged as Egypt's President Mohamed Morsi announced he had cut all diplomatic ties with Damascus. He also said he would back a no-fly zone over Syria, an intervention western diplomats say is being considered by Washington.

The video underscores the increasing organisation of foreign jihadists in the north of the country and the prominent role they are playing in some areas of the conflict almost one year after they first arrived. The Chechen-dominated group is comprised solely of foreigners who see the civil war in Syria as an important theatre for global jihad — not a battle fought to change the leadership of a nation state.

Their presence, along with homegrown Syrian jihadists, has been a key reason for the reluctance of US and other western states to support the military opposition in Syria, which remains outgunned by the regime and is struggling to hold on to parts of the country it seized during fighting over the past 12 months.

Peter Bouckaert, the emergencies director for Human Rights Watch, said the foreign groups have become more organised in recent months. "There is increasing evidence that foreign fighters are gathering under a more unified umbrella in Syria, and that the umbrella organisation may have a strong Chechen leadership," he added.

The foreign jihadists have a broadly similar worldview to the al-Qaida-aligned Jabhat al-Nusra, but operate largely independently from the group. All groups, along with the more mainstream nationalistic organisations, contest fiercely for power in northern Syrian society.

As community structures have steadily decayed over the past year, battlefield results have become an important benchmark for those seeking influence. Both the foreigners and al-Qaida groups make no secret of their determination to install an Islamic state in Syria.

The White House's decision to send military support to vetted areas of the opposition comes at the same time as extremist groups on both sides of the conflict – al-Qaida and foreign Sunni jihadists on one side, Hezbollah and Shia militants from outside Syria on the other – are playing a sharply increasing role in the conflict.

Western officials in Beirut said the decision to arm some rebels, after two years of refusal to do so, is designed largely to drive a wedge between both sides and stymie a slide into outright sectarian war that would spread beyond Syria's now fragile borders.

"The US does not want Chechens or anyone else getting their hands on these missiles, or Hezbollah getting its hands on important parts of the country," one official said.