- Madleen yacht carries symbolic aid for besieged Gaza Strip
- Israel says naval blockade vital to its national security
- Yacht with activist crew currently off Egyptian coast
Operated by the pro-Palestinian Freedom Flotilla Coalition (FFC), the British-flagged Madleen yacht set sail from Sicily on June 6 and is currently off the Egyptian coast, heading slowly towards the Gaza Strip, which is besieged by Israel.
"I instructed the IDF to act so that the Madleen ... does not reach Gaza," Katz said in a statement.
"To the antisemitic Greta and her Hamas-propaganda-spouting friends, I say clearly: You'd better turn back, because you will not reach Gaza."
Climate activist Thunberg said she joined the Madleen crew to "challenge Israel's illegal siege and escalating war crimes" in Gaza and highlight the urgent need for humanitarian aid. She has rejected previous Israeli accusations of antisemitism.
The Madleen is carrying a symbolic quantity of aid, including rice and baby formula, the FFC has said.
FFC press officer Hay Sha Wiya said on Sunday the boat was currently some 160 nautical miles (296 km) from Gaza. "We are preparing for the possibility of interception," she said.
Besides Thunberg, there are 11 other crew members aboard, including Rima Hassan, a French member of the European Parliament.
Israeli media have reported that the military plans to intercept the yacht before it reaches Gaza and escort it to the Israeli port of Ashdod. The crew would then be deported.
In 2010, Israeli commandos killed 10 people when they boarded a Turkish ship, the Mavi Marmara, that was leading a small flotilla towards Gaza.
