When summer began, Ward’s* biggest worry was her sick boyfriend.

A Syrian with a gentle voice, and all her identity documents in order, Ward thought she could convince doctors in Istanbul, where she lived, to see her boyfriend, another refugee, without papers.

Instead, the hospital alerted the police, who came and arrested them both. Days later, Ward made a panicked phone call from Binkilic deportation centre on the outskirts of Istanbul to a hotline operated by refugee rights activists to tell them she was about to be deported.

“If al-Nusra get me, they will kill me,” Ward said in a voice message from the jail, referring to the anti-government militant group, now known as Hayat Tahrir al-Sham (HTS), who control the province bordering Turkey.

As the war barrels onward in northern Syria, refugees in neighbouring Turkey fear even walking the streets. Istanbul police have launched a crackdown on ID papers that has seen thousands swept up and deported back to the warzone.

With public opinion turning against the 3.6 million Syrian guests, Turkey has reversed its long-standing “open door policy” to capitalise on bipartisan calls to send Syrians home.

Facing accusations of refoulement, the UN Refugee Agency, UNHCR, has ignored the most vulnerable cases.

Ward, who is a transgender woman, was legally residing in Istanbul and had been assigned a UNHCR protection officer who specialises in cases of LGBT refugees.

While detained in a cell full of men, she feared a worse fate could befall her in Syria. Ward contacted friends who contacted UNHCR, and a legal aid counsellor was dispatched.

But they were too late – she was deported the next day.

Less than 100 metres after crossing the border, Ward was taken by HTS security officers.

“They humiliated her after finding videos of her with men on her phone, and asked her why she shaved her arms and legs,” says Kenan Shami, who was with Ward for the 20-hour bus ride to the border.

Shami told the Guardian that militants handcuffed Ward, tied a bag over her head, and forced her into the trunk of a taxi. She has not been heard of since.

Forced returns to a warzone violates both international law and Turkish law, which allows a 15-day window to appeal a deportation to the Constitutional Court.

Protest against refugee deportations in Istanbul in August. Photograph: Asmaa Al Omar/The Guardian

But lawyers say after the recent crackdown, authorities are exploiting a legal loophole by coercing refugees to sign papers saying they want to return voluntarily, and carrying out deportations so quickly advocates say they can’t keep pace.

“We see none of the legal waiting periods being respected. It normally takes months, but now we see deportations being carried out in as little as 48 hours,” said human rights lawyer Yasemen Öztürkcan. “It’s not normal, and it’s not legal.”

A spokesperson for the Istanbul governor’s office denied that Syrians are forcibly returned from the dense city of 18 million, and insisted the government was only referring them to other provinces for registration.

Lawyers reject those claims. “They say they are taking them to another province, but our clients call us from Syria,” said Öztürkcan.

Turkish officials say around 340,000 refugees have voluntarily returned to Syria. UNHCR, which is mandated to oversee the process, has only monitored around 62,000.

Refugee advocates warn that officers in deportation centres have kept refugees detained until they relent and sign the papers put in front of them.

The Istanbul Bar Association has brought 180 complaints against police officers for improper use of refugees’ voluntary return forms.

UNHCR officials in Ankara, Geneva, and New York refused the Guardian’s requests to comment on any cases of deportations from Turkey to Syria.

Police raids and identity checks launched on 12 July have mostly targeted groups of Syrian men in dense Istanbul neighbourhoods.

Ward brought up her fears of being stopped on the street and deported to Syria frequently, said her former roommate, Sami. The two lived in an LGBT shelter in Istanbul, and went together to their UNHCR asylum appointments.

“The NGOs are asleep, they are useless,” Sami said. “Ward and I spoke to many organisations about deportations and they didn’t believe us, they seem unable to believe that the Turkish government is really doing this.”

Ward was “a beloved person, who would never hurt anyone,” Sami said. “Her dream was just to be safe, because her siblings and family were threatening her saying they want to kill [her] because [she’s] queer.”

To cope with fears of visibly going through her gender transition process, Ward chose to maintain a more masculine look.

“On the outside people saw a man, but on the inside there was a complete woman in every sense of the word, and Ward preferred to be called ‘she’,” Sami said.

Ward’s friends haven’t heard from her since she lost what safe haven she had in Turkey, and now fear she faces certain death in Syria.

UNHCR today finds itself in a difficult position, having to balance its mandate to protect refugees with maintaining engagement with the Turkish government, its main partner. The agency began building its reputation in Turkey when it intervened during the Kurdish refugee crisis in the 1990s. In 2012 thanks in part to this relationship,Turkey passed major reformsestablishing a temporary asylum protection regime for Syrians.

“Humanitarian work is not supposed to be political, but the reality is political,” said Metin Çorabatır, who was UNHCR’s chief spokesperson in Turkey from 1995 until 2013.

“I would hate to be in their shoes, but if I were at UNHCR in today’s circumstances – if we were able to establish such accusations – then I might say, ‘OK, we have confirmed some violations, and we are negotiating with the Turkish government over our concerns, and have asked them not to repeat them’,” said Çorabatır, “but silence would be the worst option.”

UN personnel are bound by a strict code of silence forbidding them to speak publicly about their work. Speaking to the Guardian on the condition of anonymity, some suggested the relationship with the government had become too close.

“People’s rights are being violated right under the nose of the UN and we’re not doing the right thing because there is a worrying amount of pressure on maintaining good relations with the Turkish government,” one UN staff member told the Guardian.

Another said: “The UN has to toe a line while operating in Turkey. If we want to run projects without government restriction then it’s best not to offend them, even if that means not publicly condemning the deportations outright – even if they contravene international humanitarian law.”