More than 400 people in a global flotilla - including 11 Australians - were released on Thursday after being intercepted by Israeli forces at gunpoint in international waters on Tuesday.
One of the Australians on board the flotilla, Zack Schofield, said many in the group were treated poorly in prison.
"Many of us haven't eaten for days. We were denied water for two days," he said in a statement.
"I have friends that were shocked with tasers, stun guns for extended periods of time just on entry to prison."
Melbourne flotilla participant Neve O'Connor said she was physically assaulted during her time in detention.
"My shoulders were almost dislocated, I was kneed in the face again, I was kneed in the stomach," she said on social media after her release.
"I had my hands zip-tied behind my back for so long and it was so tight I almost started vomiting."
A spokesperson for Australia's Department of Foreign Affairs and Trade said consular officials had met with the Australians when they were released, but none were seriously injured.
"No Australians required immediate medical attention, beyond the provision of basic first aid supplies. Access to medical treatment remains available," the statement said.
Their release follows condemnation of Israeli National Security Minister Itamar Ben-Gvir, who posted a video of himself taunting the detainees while they knelt with their heads on the ground.
The "shocking" video prompted a public rebuke from Foreign Minister Penny Wong, who summoned Israel's ambassador to Australia Hillel Newman for an explanation.
Mr Newman said the activists were "certainly safe" and had access to consular officials while in detention.
"No one is in harm's way ... the dealing with them was very sensitive," he said on Thursday.
The Foreign Affairs spokesperson said: "Along with other countries, Australia has raised our concerns with Israeli authorities about the treatment of detainees and delays in providing consular access in line with international obligations."
A statement from the flotilla's Australian contingent said members were being forensically examined in hospital in Istanbul and will meet with lawyers to document their experience.
They will then return to Australia in coming days.
Federal minister Tanya Plibersek said the actions of Israel's minister was shameful.
"It was absolutely disgraceful behaviour, and I'm very pleased to say that the foreign minister has said that in the strongest terms to the Israeli government," she said.
"Our Australian ambassador in Israel has made the position of the Australian government very clear, that this behaviour is acceptable, completely unacceptable."
Greens senator Nick McKim said stronger actions were needed from the federal government.
"This demands the strongest possible response from our prime minister and our foreign minister, a far, far stronger response than they've delivered to date," he told ABC Radio.
"That is abhorrent treatment of people by a senior figure in the Israeli government. People are being degraded, they're having their human rights abused. It is effectively a form of torture."
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