DAMASCUS: A major Syrian rebel group is using dozens of captives in metal cages as "human shields" in the largest opposition stronghold on the outskirts of Damascus, a monitor said Sunday.

Jaish al-Islam, regarded as the most powerful rebel group near the capital, has put regime soldiers and Alawite civilians it was holding in metal cages, the Syrian Observatory for Human Rights (SOHR) told AFP.

The group then placed these cages in public squares in the Eastern Ghouta region in an attempt to "prevent regime bombardment", Observatory head Rami Abdel Rahman said.

"Jaish al-Islam is using these captives and kidnapped people — including whole families — as human shields," he said.

Government forces regularly bombard the Eastern Ghouta area, from where rebel groups fire rockets into the capital.

On Friday, at least 70 people were killed and 550 wounded in regime bombardment of Douma, a large town in the area.

Read: Attacks on Syria rebel strongholds kill 91

A video published by opposition news outlet Shaam Network showed cages of men and women, about five people in each, being transported on the backs of three lorries through war-ravaged streets as young children rode by on bicycles.

Speaking to camera, both men and women asked government forces to stop shelling Eastern Ghouta.

"Your women are our women. If you want to kill my mother, you will kill them too," a dark-eyed teenage boy said outside one of the trucks.

Abdel Rahman said most of the civilians were kidnapped by Jaish al-Islam two years ago outside Adra al-Ummaliyah, a regime-held neighbourhood in Eastern Ghouta.

A Jaish al-Islam spokesman was not reachable for comment.

Both regime forces and rebel groups have been criticised by rights groups for indiscriminate attacks on civilians in Syria's war, which has killed more than 250,000 people since it began in March 2011.

Al Qaeda chief urges militant unity against Russia in Syria

Al Qaeda leader Ayman al-Zawahri called on Muslim supporters to band together to confront the threat from the West and Russia in Syria and Iraq, the latest recording suggesting greater unity between Al Qaeda and the self-styled Islamic State (IS).

"The Americans, Russians, Iranians, Alawites, and Hezbollah are coordinating their war against us — are we not capable of stopping the fighting amongst ourselves so we can direct all our efforts against them?" Zawahri said in an audio recording released on the Internet on Sunday.

It was not clear when the recording was made but references to Russian aggression suggest it was made after Russia, an ally of Syrian President Bashar al-Assad, launched air raids against opposition groups and IS in Syria on September 30.

In a recording released in September, Zawahri dismissed IS and its leader Abu Bakr al-Baghdadi as illegitimate but said his followers would join them in fighting the Western-led coalition in Iraq and Syria if possible.

"My mujahideen brothers in all places and of all groups ... we face aggression from America, Europe, and Russia ... so it's up to us to stand together as one from East Turkestan to Morocco," Zawahri said.

IS, the ultra-hardline group that controls large parts of Iraq and Syria, has called for a holy war against both Russia and the United States (US) in response to air strikes on its fighters in Syria.

Any cooperation between Al Qaeda and IS would further complicate efforts to stabilise the Middle East, where militant groups have gained influence and escalated attacks since the Arab uprisings of 2011 toppled autocrats who had contained them.

Also read: Zawahiri pledges allegiance to new Taliban chief

IS claims murders of Syrian activist, friend in Turkey: video

Daesh or the self-styled Islamic State (IS) jihadist group on Sunday posted a video claiming responsibility for the brutal murders of a Syrian anti-IS activist and his friend in southern Turkey last week.

The video posted online said IS "slaughtered" Ibrahim Abdul Qader, 20, and fellow media activist Fares Hamadi in Sanliurfa on Friday "after they conspired with the Crusaders against the IS".

Abdul Qader had been working with the Raqa is Being Slaughtered Silently (RBSS) activist group, which sheds light on IS atrocities in areas under jihadist control in Syria.

The video displayed a series of news reports about the RBSS group and its anti-IS activities.

It closed with amateur video footage of a man who appeared to be Hamadi, his throat slit.

Abdul Qader's body was not shown.

Abdul Qader and Hamadi's bodies had been found at the latter's home in Sanliurfa on Friday morning by another friend, according to RBSS member Abu Mohammad.

The group's activists have been killed by IS inside Syria in the past, but this is the first time a member had been murdered outside the war-torn country, Abu Mohammad said.

Turkey has long been accused by Syrian opposition activists, Kurdish fighters and sometimes even Western partners of allowing IS members to slip back and forth across its 911-kilometre frontier with Syria.

Bloody bomb attacks in southern Turkey, including one in July that claimed 32 lives in Suruc, have been blamed on IS.

The group has never claimed responsibility for the blasts.