An 18-year-old Saudi woman being detained in Bangkok having fled from her family after renouncing Islam fears she will be killed if she is repatriated, according to a close friend who said the threats to her life are real.

Rahaf Mohammed al-Qunun has barricaded herself in her hotel room for fear that Thai immigration officials, who have gathered outside her door, would force her on to a plane to leave the country. Thai immigration officials have confirmed she has been denied entry to the country.

The Guardian has confirmed Qunun had a three-month multiple-entry tourist visa for Australia, where she said she was intending to seek asylum.

Qunun maintains she will be killed if she is returned to Saudi Arabia and has said she will not leave until she can see the United Nations High Commissioner for Refugees, according to Phil Robertson, Human Rights Watch’s Asia deputy director.

Robertson said that in an “important victory” for Qunun, Kuwait Airlines flight KU412 to Kuwait, which she feared she would be forced to board, left Bangkok without her. In a video posted after the plane departed, she said: “I am Rahaf, the plane has departed, I am in the hotel, I need a country to protect me as soon as possible. I am seeking asylum.”

Kuwait Air officials, #Thai Immigration officials and others are outside #Rahaf's door, demanding she open it. She is refusing, saying that she wants to see UN #Refugee Agency @Refugees & demanding #Thailand let her seek asylum. Time ticking down, flight leaves in 29 minutes. pic.twitter.com/wQ266wWFwX — Phil Robertson (@Reaproy) January 7, 2019

Qunun said she was trying to escape from her family because they subjected her to physical and psychological abuse. She has appealed for help from Europe, the US, Canada and Australia.

“My family is strict and locked me in a room for six months just for cutting my hair,” she said, adding that she was certain she would be imprisoned if sent back. “I’m sure, 100%, they will kill me as soon as I get out of the Saudi jail,” she said, adding that she was scared and losing hope.

A 20-year-old friend of Qunun, whom the Guardian has chosen not to name and who recently moved from Saudi Arabia to Australia, said the threats to her were real. “She’s ex-Muslim and has a very strict family, they’re using violence with her and she faced sexual harassment,” she said. “She received a threat from her cousin – he said he wants to see her blood, he wants to kill her.”

Calling @KuwaitAirways - the entire world is watching you. Do not allow the deportation to Kuwait of @rahaf84427714 - you will be complicit in endangering her life. Do not allow this! #SaveRahaf https://t.co/rhvlzj7rHS — Mona Eltahawy (@monaeltahawy) January 7, 2019

“If they didn’t kill her they couldn’t go [around in] public after this [Qunun renouncing the Muslim faith], so they have to do it,” the friend said. “It’s like: If you’re a man you should prove it. If they don’t kill her they can’t go outside and see other men.”

Qunun’s friend has lived in Australia for three months, and said she was seeking asylum there after being abused in Saudi Arabia. She said she had known Qunun for a year, after connecting with her online. “She’s an activist, she’s a feminist,” she said. “There are lots of feminist groups [in Saudi Arabia].

“They gather online to protect each other, help each other. [For example] I saw a woman giving money to shelters, food, donations. Even buying tickets for women escaping.”

Georg Schmidt, Germany’s ambassador to Thailand, tweeted his support for Qunun, saying: “We share the great concern for Rahaf Mohammed and are in touch with the Thai side and the embassies of the countries she approached.”

Sarah Hanson-Young, a senator from South Australia, called on Australia to issue her with emergency travel documents.

Robertson said there was no doubt Qunun needed refugee protection and that the UNHCR had to be given immediate access to the hotel.

“Rahaf faces grave harm is she is forced back to Saudi Arabia so she should be allowed to see UNHCR and apply for asylum, and Thailand should agree to follow whatever the UN refugee agency decides,” Robertson told the Guardian.

“She’s desperately fearful of her family, including her father who is a senior government official, and given Saudi Arabia’s long track record of looking the other way in so-called honour violence incidents, her worry that she could be killed if returned cannot be discounted,” he said.

Video from @rahaf84427714 just sent from her hotel room at the #Bangkok airport. She has barricaded herself in the room & says she will not leave until she is able to see #UNHCR. Why is #Thailand not letting @Refugees see her for refugee status determination? @hrw #SaveRahaf pic.twitter.com/3lb2NDRsVG — Phil Robertson (@Reaproy) January 7, 2019

“She has clearly stated that she has renounced Islam which also puts her at serious risk of prosecution by the Saudi Arabian government.”

Qunun, from Ha’il, in north-west Saudi Arabia, said she was stopped by Saudi and Kuwaiti officials when she arrived at Suvarnabhumi airport on Sunday and her travel document was forcibly taken from her, a claim backed by Human Rights Watch.

The Saudi embassy in Bangkok said Qunun was being held for not having a return ticket, and that she still had her passport, a claim denied by Qunun.

“They took my passport,” she said, adding that her male guardian had reported her for travelling “without his permission”.

She spent Sunday night in an airport hotel and tweeted that officials were posted outside her door to stop her leaving. On Monday morning she said she was trying to claim asylum in Thailand.

Thailand’s immigration chief, Surachate Hakparn, said Qunun had no money or return ticket when she arrived at the airport.

“She ran away from her family to avoid marriage and she is concerned she may be in trouble returning to Saudi Arabia.”

Thai officials had been sent to take care of her and were coordinating with the Saudi embassy, he said.

Qunun would be sent back to Saudi Arabia on Monday, he said. “It’s a family problem.”

The Saudi embassy in Thailand and officials in Riyadh could not be reached for comment.

Agence France-Presse contributed to this article