The Department of Foreign Affairs and Trade (DFAT) said it was liaising with Israeli authorities and was on standby to assist the detainees.

DFAT said it had previously issued warnings to Australians not to attempt to breach the naval blockade because of the safety risks.

Families of Australians speak out

A protest organised by Students for Palestine briefly blocked traffic outside Melbourne’s Flinders Street railway station on Thursday night, while speakers addressed a crowd of approximately 200 people.

Flotilla’s communications jammed

They said several of their vessels had been boarded by Israeli forces, including the Spectre, Alma, Sirius and others.

“It does seem at this stage they are unprepared to sink the vessels or to kill anyone.”

“There is no sea access to Gaza. Israel has a naval blockade in place along the coast of Gaza. Don’t join others seeking to break the blockade,” DFAT’s Smartraveller website says. “Previous attempts to break the blockade have resulted in death, injury, arrest or deportation of foreigners.”

Before the interceptions, assistant foreign affairs minister Matt Thistlethwaite said he was concerned about the safety of Australians on the flotilla and called on Israel to refrain from “any unlawful or violent act against the flotilla”.

Organisers say flotilla ‘will continue undeterred’

The flotilla had hoped to arrive in Gaza on Thursday if it was not intercepted.

World reacts to Israel’s interception

In Berlin, protesters swarmed the Berlin Central Station and chanted slogans like “Free Palestine”.

Demonstrators protest in solidarity with the Palestinian people and over Israel’s navy intervention against the Global Sumud Flotilla outside the foreign affairs ministry, in Athens, Greece. Source: AAP / EPA / Orestis Panagiotou

Thousands of people took to the streets in Italy to protest against Israel’s interception of the flotilla, which has an Italian contingent on board.

Türkiye’s foreign ministry called Israel’s “attack” on the flotilla “an act of terror” that endangered the lives of civilians.

“Keir Starmer has a serious role to play. With British citizens and British-flagged ships involved, he must not revert to silence as usual.”

All navigation and communication devices went down in what one organiser on board described as a “cyber attack”.