TEL AVIV — Israel made clear on Thursday that if a new flotilla of pro-Palestinian activists sought to break its naval blockade of Gaza like the one a year ago when its commandos killed nine people, the Israeli military would use force again, including boarding the ships and confronting the activists.

“We will do anything we have to do to prevent a boat from breaking the blockade,” a top naval official said in a briefing for foreign journalists. “If there is the same violence against our forces on board, there is a pretty good chance there will be injuries.” The official spoke on the condition of anonymity under Israeli military rules.

On Israel Radio on Thursday, the military’s chief spokesman, Brig. Gen. Yoav Mordechai, said the army would stop any ship from entering Gaza. General Mordechai added, “There is an unequivocal directive from the government to enforce the naval blockade that is recognized by international law, and we will not allow it to be broken.”

The statements seemed part of a heightened effort to stop another flotilla and to pre-emptively explain Israel’s position if violence ensues.