Eleven Australians were among 400 people taking part in the Global Sumud Flotilla to Gaza before being intercepted by Israeli forces at gunpoint in international waters on Tuesday.
No one has heard from the Australians since, but a social media post by Israeli national security minister Itamar Ben-Gvir overnight showed him gloating over flotilla participants as they are forced to their knees by guards.
In the video, Mr Ben-Gvir walks through a crowd of detainees kneeling with their heads on the floor as he smiles and berates a man whose hands are zip-tied.
It is unclear whether any of the Australians are in the video, but Jacinta McEwen - whose son Surya McEwen has taken part in the aid effort - said she was left horrified.Â
"I'm absolutely outraged that Ben-Gvir is bragging about basically torturing the participants," she told AAP.
"I'm really worried (Surya) is going to be hurt."
Mr McEwen has previously been detained by Israeli forces after taking part in other flotilla attempts.
Last time, he had his head slammed against a steel wall and a dislocated shoulder, a broken collarbone and broken ribs from being kicked in the chest, his mother said.
A report from Adalah Lawyers - a legal team acting for Arab minority rights in Israel - said the latest group of flotilla participants have passed the initial processing stage of Israeli immigration and are being transferred to Ketziot Prison.
The lawyers have received complaints from the activists, including from at least three people who have been hospitalised and released, about the use of tasers and rubber bullets, sexual harassment and degradation.
But Bernadette Zaydan, a lawyer representing some of the Australians, has yet to receive clarity from Israeli or Australian authorities.
"The Israeli military is not forthcoming with information and they seem to do this to intentionally waste our resources," she told AAP.
The Australian cohort is expected to face a tribunal before being deported, though the lawyers are struggling to find out where they could end up, Ms Zaydan said.
Foreign Minister Penny Wong has called for the release of the Australians after condemning the video posted by Mr Ben-Gvir.
"The images we have seen posted by Israeli Minister Ben-Gvir - who Australia has sanctioned - are shocking and unacceptable," Senator Wong said on X.
"We condemn his actions and the degrading actions of Israeli authorities towards those detained."
Senator Wong told the Department of Foreign Affairs to call in Israel's ambassador to Australia, Hillel Newman, to reinforce her message.
Dr Newman is expected to meet with departmental officials on Thursday after Israeli Prime Minister Benjamin Netanyahu and foreign minister Gideon Sa'ar condemned their colleague's actions as "not in line with Israel's values".
But a member of the flotilla's Australian delegation, Subhi Awad, said this was not enough.
"(Senator Wong) has not condemned the actual kidnapping of our people, she's just said the abuse is bad," he said.
"Well, everybody knows the abuse is bad, but clearly kidnapping them is also not only abhorrent but illegal."
While Ms McEwen remains concerned for her son, she is also proud of him.
"He's very brave and he's got a very big heart," she said.
"He's actually a big sweetie, he's not an angry activist-y sort and he deeply cares for people.
"Our government should be making sure aid is getting in, but instead it's our sons and daughters, like Surya, who are forced to do this."
