Disturbing videos of life inside the Islamic State have emerged, showing boys as young as five being trained in urban warfare skills and men bartering over Yazidi slave girls. The videos are being smuggled out of the ISIS-held territory by various underground groups committed to documenting the oppression waged by the jihadists.

In one video a blond boy of around five years old is seen running through the streets of Raqqa armed a with pellet gun. He laughs as he dodges pretend enemy fire and moves from post to post. What would look anywhere else like mere war games is believed to be a training exercise for the young boy, as two men, believed to be Islamic State fighters, are seen to look on with approval.

According to the Daily Mail, the video was shared online by Raqqa Is Being Slaughtered Silently, an activist group which documents life in the city under the oppressive Islamic State regime. The group covertly uses mobile phones to film and take photos of atrocities committed in Raqqa by ISIS.

“We were activists against the Assad regime when we started, but after our city was freed, and ISIS took over our freedom, we just decided to launch this campaign to expose all the crimes that ISIS do,” former medical student Abu Ibrahim Raqqawi told Vice News. He was forced to flee the city after documenting a crucifixion.

Charlie Winter, a spokesman for anti-extremist think tank The Quilliam Foundation said: “This video is yet more evidence of Islamic State seeking to indoctrinate children from a very young age in an attempt to entrench its hold over the region. Such footage is worrying, in particular because it renders apparent the fact that IS’ legacy will be long-term, even if it was to collapse tomorrow.”

Another video documents men bartering over Yazidi slaves. Sitting on sofas in a living room, a man wearing a white cap turns to the camera and says “Today is slave market day. Today is the day where this verse – “… except with their wives and the (captives) whom their right hands possess, for (then) they are not to be…” today is distribution day, God willing. Each one takes his share.”

His friend chimes in “I swear man I am searching for a girl. I hope I find one.”

Another exclaims “Today is the day of (female) slaves and we should have our share!”

And in the background, yet another yells “Where is my Yazidi girl? Where is my Yazidi girl?!”

The white capped man explains the rules: “Whoever wants to sell his slave, whoever wants to give his slave as a present, everyone is free to do what he wants with his share. Whoever wants to sell, I can buy my brothers. Whoever wants to sell his slave, I buy. Whoever wants to sell his own slave, I buy. And if you want to give her as a gift, also I take her.”

They then descend into bartering over the girls, with exchanges for a Glock pistol and prices of up to around £500 offered. One man demands to be able to check the 15 year old girl he is bidding for, to make sure she has teeth. “If she doesn’t have teeth, why would I want her?” Others offer higher prices for girls with blue or green eyes.

The video was translated by the Arabic channel Al Aan TV, who claims that it was shot in Mosul, Iraq’s second largest city. It is thought that the women and children were captured in Sinjar town, where fighters claim to have divided the captives amongst themselves “according to Sharia law”.

Stories told by the Yazidi slaves of their plight have emerged over recent weeks. One woman managed to contact Iraqi peshmerga fighters, pleading with them to ask the West to bomb her brothel to end her misery and that of the other sex slaves held captive. She said she had been raped more than 30 times in just a few hours, leaving her unable to go to the toilet. She was so traumatised that she told of plans to commit suicide even if freed.

Another girl, a 15 year old killed her first owner and escaped from a second. The girl was captured in Sinjar and eventually taken to Raqqa where she was sold to, and married a man. After obtaining a gun from his aggrieved housekeeper, she shot him and fled. Unsure where to go, she was again captured and again sold, this time for £620 to a Saudi fighter who planned also to convert her to Islam and marry her.

She was able to escape his clutches after tipping a powdered drug into tea served to him and his accomplices. Once she had slipped away, she found a man willing to drive her to Turkey to meet her brother. She and her brother have now returned to northern Iraq, paying smugglers £1,250 to get them across the border.