The last time Rûken Renas saw her friend Anna Campbell, they were heading by coach into Afrin, northern Syria, to help defend the besieged Kurdish city from Turkish attack.

“We had stopped for a break and I spotted her chewing sunflower seeds in the sun,” recalled Renas, a 26-year-old Londoner who asked to be called only by her Kurdish nom de guerre for fear of legal reprisals when she returns to the UK. “When I asked what she was planning to do, she said, ‘I’m going to fight.’”

But with Afrin on the brink of being completely overrun by Turkish-backed rebels, plus rumours of torture and mutilation of captives, Renas had heard her commanders were withdrawing female fighters for their safety. “When I told her this she just laughed and said, ‘We’ll see when I get there.’ Then she gave me a big hug and got on her coach. She was killed a week later – one of the bravest women I have ever met.”

Anna Campbell, 26, from Lewes, East Sussex, became the first British woman to die while fighting alongside Kurdish forces in Syria when the convoy she was travelling in was hit by a Turkish airstrike on 16 March.

Now, Renas – one of a handful of British women fighting with the all-female Kurdish women’s protection units (YPJ) in Syria – has come forward to urge Britain to do more to support Syria’s Kurds as they defend their homeland from Turkish attack or “thousands of people could die”.

“There needs to be more international pressure to stop Turkey’s incursion into Rojava,” she says, referring to the semi-autonomous heartland of Syria’s Kurds. “Rojava’s [feminist and socialist] revolution is under threat of being completely extinguished by Turkey. We need government support, we need civil support. The world must not remain silent on what is happening here.”

Renas spent almost a month over two deployments in Afrin at the height of a seven-week siege that ended last Sunday as Turkish-backed rebels took control of the city.

“I have never seen anything like it in all my life,” she said from her military base in the Kurdish city of Qamishli, where her unit has repaired since escaping the city. “It was chaos. The bombing was really heavy, especially just before the city fell. They hit the hospital, people were fleeing. I was helping out at the hospital and bodies were just coming in day after day. Seeing women screaming, fainting. Mothers who have lost their sons, daughters who have lost their fathers. These were civilians, not soldiers. It was heartbreaking.”

Rûken Renas. Photograph: Collect

Describing herself as a Marxist, the computer technician says she deployed to Afrin with the International Freedom Battalion (IFB), an armed group of foreign communists, anarchists and socialists fighting Isis under the aegis of Syria’s Kurdish people’s protection units (YPG) and its all-female affiliate the YPJ.

Turkey launched its ground and air offensive – codenamed Operation Olive Branch – on Afrin on 20 January in an attempt to prevent the YPG from establishing a foothold along its border. Ankara argues that the YPG is linked to its own Kurdistan Workers’ party (PKK), which has waged an insurgency on Turkish soil since 1984. The US, EU and Britain, however, do not consider the YPG a terrorist group, and have supported the Kurds’ fight against Isis since 2014.

There are already suggestions that Afrin holds terrible secrets. In early February, Syrian Kurds accused Turkish-backed rebels of mutilating then filming the body of a YPJ fighter after a video emerged of her corpse. “I don’t think women were in any more danger than men,” says Renas. “But how we die is different.”

She claims the Turkish-backed rebels employed similar tactics to Islamic State. “They would ignore YPG points, bypass them, and make a beeline straight for the women-only YPJ points. Where captured YPG male fighters would often be beaten or tortured to death, for women it would be much worse. I don’t even want to repeat it, but just really vicious, nasty things. Sexual stuff, not just violence. I think it’s just a deep hatred for women who are free.”

Nevertheless, she too convinced her commander to allow her to stay in Afrin to guard a women’s refuge on its outskirts until it fell last Sunday, when she caught one of the last convoys out of the city – the same day Campbell was killed.

Renas says she was first drawn to Syria after seeing the atrocities Isis were committing against civilians in Iraq and Syria. “My mother’s family are from Iraq and watching Isis try to destroy not just the Levant, but attack Europe as well, made me so angry,” she said. “I felt I had to do something.”

But rather than travel to Iraq, she chose northern Syria, so powerfully struck was she by the grassroots egalitarian and feminist revolution that has risen there from the rubble of Syria’s civil war. “They have built a system of direct democracy and gender equality in the heart of the Middle East,” she says. “The region has suffered war and oppression for decades. But in Rojava life is completely different. The people here are tasting freedom for the first time, not just the Kurds, but Arabs and Assyrians too.”

She adds: “I come from a communist family and have grown up around communism and its ideas my whole life. I went to Rojava to show international solidarity and to defend people from fascism and the forces of tyranny and oppression.”

She arrived in Rojava in September, where she completed the IFB’s mandatory month-long military training course – in which new recruits learn basic Kurdish, weaponry and battlefield tactics on top of a crash course in the ideology of Rojava – and joined an infantry division, comprising leftist fighters from around the world.

There she was given the nom de guerre Rûken Renas – Kurdish for “she who smiles” – and spent her first few months working in civil society, moving from town to town to help set up communes and women’s groups, and providing aid to bereaved families.

It was during this time that she met Campbell, who was attached to YPJ International, a separate all-female battalion of foreign fighters. “Anna and I were the same age, from the same country, both leftwing, although she was an anarchist and I’m a communist,” she says. “We got on really well.”

But, she says, Campbell was growing frustrated that her YPJ commanders were refusing to let her fight. “They are reluctant to send foreign women to battle because we have other skills, like communication, technology or social media skills,” says Renas. “But all she wanted was to defend Rojava and the revolution. And when Turkey attacked Afrin, she kept badgering. She was immensely strong and never took any crap. In the end, they gave in.”

While she managed to persuade her commanders to send her to Afrin, she describes getting to the front as “a constant battle”. “A lot of people think it’s like Call of Duty,” she adds. “In fact, I only know one foreign fighter with a confirmed kill. No, there’s a lot of waiting, dodging bullets and airstrikes. But when I did get there, it was heavy.”

Renas says she and her colleagues now face a tense wait to see what Turkey does next. “The thinking on the ground is that they’ll attack Manbij next and make their way inwards. If they come to the rest of Rojava, it’s going to be a complete and utter bloodbath. Thousands could die.”

She says she would like to stay in Rojava, and fight if she has to, for some months before she returns back to the UK.

“I do want to go home but I can’t say when because I’m worried about prosecution,” says Renas. “I know that other volunteers have been persecuted by the state for going to fight Isis,” she says. Two men have so far been charged under the terrorism act in the UK for joining the YPG.

“I don’t want that and I don’t want to go to jail. But if I have to then I’ll do it. It would still be worth it. Prosecuting me, and others like me, would just show the hypocrisy of the British state,” she adds.

“It’s been involved in many foreign conflicts abroad, not least Iraq which was an illegal war. Yet, I find the fact that British citizens are supposedly not allowed to join foreign wars quite rich coming from the British government.”