Activists on board a flotilla of vessels sailing toward Gaza say they are are prepared for the Israel navy to intervene as they approach the besieged Palestinian territory, after a tense night in the Mediterranean Sea.

The Global Sumud Flotilla, with Greta Thunberg aboard, consists of about 50 boats and 500 activists from 44 nations, including at least six Australians involved.

“I can’t even begin to put into words how it feels,” Sydney content creator Abubakir Rafiq, who is aboard Spectre, said in an Instagram post.

”It’s so close and everything has led to this moment right here, the final hours, the final part of the journey.”

Rafiq said the flotilla hoped to “break the siege” and “announce that this humanitarian corridor has opened up” as a result of their efforts.

Matt Thistlethwaite, Australia’s assistant minister for foreign affairs, said he was “very concerned about the safety of these people” and about what the next 24 hours could have in store, as the group approach Gaza.

“I’m deeply concerned by the alleged drone attacks on the Global Sumud Flotilla and the risks to the safety of Australians and other passengers onboard,” he said in a statement.

”Australia calls on all parties to respect international law and international humanitarian law, and to refrain from any unlawful or violent act against the Flotilla.

“We understand people are distressed and want to respond to the humanitarian catastrophe in Gaza – we also want to see critical aid being delivered.”

The flotilla is carrying a symbolic amount of aid and has remained undeterred in its mission to break the Israeli blockade of the coastal strip and reach Palestinians.

“Every minute we advance a little more,” Thiago Ávila, one of the flotilla leaders and spokespeople, told reporters on Wednesday in an online news conference from aboard the Alma, one of the flotilla’s motherships.

The ships were sailing in international waters north of Egypt on Wednesday morning and had entered what activists call a “danger zone” – which Israeli authorities had warned them not to cross and where the Israeli navy had stopped attempts by other flotillas in the past.

Overnight, the activists said two Israeli warships aggressively approached two of their boats, circling around them and jamming their communications, including the live cameras on board.

“It was an intimidation act, they wanted us to see them,” said Lisi Proença, another activist who was on board the Sirius, a vessel that was targeted alongside the Alma.

After the close encounter overnight, the military vessels eventually left and the flotilla continued on its journey, broadcasting live cameras from many of its boats.

Several days earlier, the flotilla experienced a drone attack, which Australian filmmaker Juliet Lamont, who is aboard the vessel Wahoo, described as “terrifying”.

“And then some of the bombs that they were using were sonar bombs – they set off this massive noise.”

Another Australian on board, Surya McEwen, said they had all undertaken extensive non-violence training.

“We’re very experienced in de-escalation and communicating in ways that are non-threatening, McEwen told The Guardian.

“We’re resolved to keep going to Gaza, if there’s any way to do so without being attacked.”

If undisturbed, the flotilla should reach the shores of Gaza on Thursday, the group said.

However, activists said that was unlikely and that they were expecting Israeli authorities to try to stop them at any moment, as they have done in past attempts.

European governments, including Spain and Italy which had sent their navy ships to escort the flotilla during part of its journey, urged the activists to turn back and avoid confrontation.

Italy has warned flotilla organisers that Israel would consider their incursion beyond the “danger zone” as a “hostile act”.

Among those concerned for the safety of those on board is Pope Leo XIV.

“From all sides, people are saying, ‘let’s hope that there will not be violence, that people are respected’,” the pontiff said.

“That’s very important.”