No longer content with executing their prisoners with knives and guns, Islamic State militants have ratcheted up their savagery by blasting a man to death with a bazooka.

Shocking video emerged today showing the captive exploding into a ball of flames after being shot with a rocket-propelled grenade that is designed to take out tanks and aircraft.

Amid sickening whoops of joy and shouts of 'Allah is greatest', the barbaric jihadis continue to fire their rifles at the dead man as they move in and surround his body.

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Condemned to horrific death: An Islamic State fighter brandishes a bazooka next to a prisoner before blasting the captive with the rocket-propelled grenade over claims he was fighting against the terror group in Syria

Taking aim: A militant points the bazooka at the prisoner who is tied to a post around 50 yards away

They then subject him to more humiliation by taking it in turns to kick the corpse while dancing and cheering in celebration.

The video was shared online by anti-ISIS activist group Syria Is Being Slaughtered Silently, which said the prisoner was accused of fighting against ISIS.

The man, named by the group as Ibrahim Shraideh, was said to be a member of the Al Shaitat tribe from the town of Abu Hamam in Syria's Deir ez-Zor province.

It said the militants were from Tunisia and Morocco.

The 80,000-strong Shaitat clan rose up against the terror group after its lightning offensive across Iraq and Syria last summer.

Sickening: The captive explodes into a ball of flames after being shot with the rocket-propelled grenade

Savage: The militants then subject the dead man to more humiliation by taking it in turns to kick the corpse while dancing and cheering in celebration

They later agreed a peace deal, but this crumbled when three members of the tribe were arrested for reportedly refusing to collect taxes for the caliphate.

Nearly 1,000 Shaitats are understood to have been masacred last year alone, including 230 who were found in a mass grave.

The footage emerged as ISIS seized full control of the ancient Syrian city of Palmyra, leaving a trail of decapitated bodies as they rampaged through the city.

The jihadis have also captured the military air base, intelligence headquarters and its notorious prison, where hundreds of inmates have reportedly been liberated.

It is the first time ISIS has claimed a city directly from the Syrian army and allied forces, which have already lost ground in the northwest and south to other insurgent groups in recent weeks.