A shadowy jihadist group claimed responsibility on Wednesday for the execution of 20 Syrian troops in the battleground city of Aleppo last month.

"God enabled the mujahedeen of the Al-Nusra Front in the city of Aleppo to capture and kill 20 heretic soldiers from the Hanano military post," the Al-Nusra Front said in a statement posted on jihadist forums.

The group, unknown in Syria until several months after the revolt against President Bashar al-Assad's regime erupted in March last year, described the soldiers as "complicit in the bloodletting of the people of Syria."

The hardline Sunni Muslim group regards members of President Bashar al-Assad's minority Alawite sect as heretics.

Its statement was accompanied by a photograph of a man dressed in fatigues and sandals leaning over a row of kneeling soldiers and pointing a pistol at one of them.

The caption reads: "Al-Nusra Front: execution of 20 soldiers of the criminal despot who took part in the killing of Muslims."

On 10 September, amateur video posted on YouTube showed rebels summarily executing at least 20 troops in Aleppo, scene of some of Syria's fiercest fighting since the launch of a rebel offensive on 20 July.

The Hanano military compound in east Aleppo was briefly captured by rebel fighters last month before they pulled back.

The Syrian Observatory for Human Rights said at the time that 20 soldiers seized in the compound were summarily executed.

The Al-Nusra Front has claimed the majority of suicide attacks carried out during the uprising, including a twin suicide bombing in Damascus that killed 55 people in May.

Its relationship with the mainstream rebel Free Syrian Army is unclear.