According to the report, Thunberg plans to take part alongside activists from more than 40 countries. The mission is expected to include dozens of vessels, aiming to breach the Israeli naval blockade.
"On August 31, we are launching the biggest attempt ever to break the illegal Israeli siege over Gaza with dozens of boats sailing from Spain," the organization said in a video posted to Instagram. "We will meet dozens more on Sept. 4 sailing from Tunisia and other ports."
In June, Thunberg was detained by the Israeli Navy during an attempt to reach Gaza on the Madleen. She was photographed receiving a pastrami sandwich from one of the sailors before being taken to Ashdod Port.
Of the 12 people aboard the Madleen, four, including Thunberg, agreed to be deported from Israel voluntarily, while all of them were banned from the Jewish state for 100 years, according to their attorneys.
Upon touching down at Charles de Gaulle Airport in France, Thunberg hosted a press conference in which she claimed she had been "kidnapped" by Israel.
A spokesman for Israeli Defense Minister Israel Katz's office declined to comment on the announcement of the new flotilla on Monday.
