Eleven Australians were among 400 people detained by Israel in international waters west of Cyprus early on Tuesday.
Video live-streamed to the Global Sumud Festival's website showed black-clad soldiers boarding the vessels while angles later taken by other flotilla participants revealed abandoned vessels bobbing in the sea as Palestinian flags fly in the wind.
Neve O'Connor, Sam Woripa Watson, Anny Mokotow, Isla Lamont, Juliet Lamont, Surya McEwen, Zack Schofield, Bianca Webb-Pullman, Gemma O'Toole, Violet Coco and Helen O'Sullivan were all confirmed to have been taken, fuelling concerns from their loved ones.
"I'm afraid but also proud of Neve. She is on an unarmed humanitarian mission to deliver life-saving aid," her father Chris O'Connor said.
"Her abduction 1200km from Gaza shows the lengths Israel will go to prevent food and medicine reaching Gaza's starving people."
The Israeli Defence Force's bombardment and starvation of Gaza has killed more than 72,000 people and destroyed the territory's infrastructure, leaving just four per cent of its cropland undamaged and accessible, according to the UN World Food Program.
Israel's foreign ministry has labelled the flotilla a "provocation for the sake of provocation".
"This flotilla is only about publicity," the ministry wrote on X.
"Israel calls on all participants in this provocation to change course and turn back immediately."
This is not the first time the Global Sumud Flotilla has attempted to deliver aid to Palestinians in the Gaza Strip.
For four of the 11 detained Australians, this is the second time they have been intercepted by Israel in two weeks while three others were imprisoned by the IDF in October.
Following his capture in late April, Mr Schofield described how fellow participants had been bashed by Israeli troops and shot at point-blank range with rubber bullets as soldiers boarded their boats more than 1000km from Gaza.
"We know that there are no limits to Israel's cruelty, no limits to the laws they will break, and our hearts and prayers are with the brave Australians and their comrades aboard this flotilla," Greens senator Mehreen Faruqi said.
The Department of Foreign Affairs and Trade is seeking confirmation of the intercepted Australians' welfare and encourages those wishing to deliver aid to do so through established channels.
"We will continue to make clear our expectation that any detainees receive humane treatment in line with international norms," a spokesperson said in a statement.
"We continue to urge Australians not to join others seeking to break the Israeli naval blockade as they will be putting themselves and others at risk of injury, death, arrest or deportation."
10°C