THESE are the dirty tactics used by suicide bombers to inflict carnage on unsuspecting victims.

CCTV footage has emerged of last Friday’s suicide bomb attack on two mosques in the Yemeni capital of Sanaa, where extremists unleashed monstrous blasts that ripped through worshippers and killed 147 people. At least 13 children were among the dead.

According to reports, authorities believe one of the suicide bombers faked an injury in order to conceal the explosives in a fake cast on his leg.

The footage shows the bomber in question on his way to the Badr mosque in Al Safia.

He can be seen hobbling on crutches before meeting a second bomber on the way.

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In the Badr mosque, the first bomber was caught by guards searching worshippers at the gate approximately 20 metres away, where he managed to detonate his device. In the ensuing panic, a second bomber entered the mosque and blew himself up amid the crowd, according to the official news agency SABA.

“I fell on the ground and when I regained consciousness I found myself lying in a lake of blood,” one survivor, Ahmed al-Gabri, told The Associated Press.

Two worshippers next to him were killed in the explosions and another died when one of the mosque’s glass chandeliers fell on him, al-Gabri said.

Another survivor, Sadek al-Harithi, said the explosions were like “an earthquake where I felt the ground split and swallow everyone.”

Large groups converge at the mosques to attend sermons at that time of day.

“We have seen bombings before in Sana,” Hassan Ali, a resident of the neighbourhood, told the New York Times.

“But this is the most horrible crime.”

Friday’s blasts left scenes of bloody devastation in the Badr and al-Hashoosh mosques, located across town from each other in Sanaa. Both mosques are controlled by the Shiite Houthis, but they are also frequented by Sunni worshippers.

Images from the scene showed a number of children among the dead.

In footage from the al-Hashoosh mosque, screaming volunteers were seen using bloodied blankets to carry away victims as a small child lay among the dead on the mosque floor.

“Blood was running like a river,” said one survivor, Mohammed al-Ansi, who said he was thrown six feet by one of the blasts at the Hashoosh mosque, where the floor was strewn with body parts.

It also reported that a fifth suicide bomb attack on another mosque was foiled in the northern city of Saada.

A purported affiliate of the Islamic State group claimed responsibility for the bombings, which also wounded 357 people — raising the alarming possibility the extremist group has expanded its presence to Yemen after already setting up a branch in Libya. Last week, the group claimed responsibility for a bloody attack on Western tourists in Tunisia that authorities said was carried out by militants trained in Libya.

If the claim is true — and the U.S. expressed scepticism — Friday’s attacks would be the first by the Islamic State group in Yemen, adding a frightening new layer to the country’s turmoil.

If Friday’s bombings were carried out by Islamic State group supporters, it could be intended as a dramatic signal to al-Qaeda, the group’s rival — effectively a challenge over turf. That raises the possibility of intra-jihadi fighting as the two compete for recruits by showing who can unleash the worst bloodshed.

In its claim of responsibility, an alleged Islamic State affiliate calling itself “Sanaa Province” warned of an “upcoming flood” of attacks.