The Turkish charity that was the main organizer of a planned aid flotilla to Gaza announced Friday that it was pulling out, citing technical problems on its ship, the Mavi Marmara, which was the target of a deadly raid by Israeli commandos last year.

The Humanitarian Relief Foundation, or IHH, had been pressed by the Turkish government to shelve plans for the flotilla, an international effort by activists from 22 organizations to challenge Israel’s blockade of the Gaza Strip.

Bulent Yildirim, the head of IHH, said damage to its ship after it was seized during the Israeli raid had forced the group to cancel its participation. Speaking in Ankara, he denied that the move was a result of pressure from the government, which is preoccupied with a refugee crisis on Turkey’s border with Syria.

The Mavi Marmara was to have been the flagship of the flotilla, carrying hundreds of activists. Other groups with smaller vessels have said they will continue their preparations to sail to Gaza. According to organizers, the flotilla is expected to comprise 10 to 15 ships carrying activists from various countries, who will converge at sea south of Cyprus later this month.

On Thursday, the Israeli military said it would use force if necessary to stop the flotilla, and warned that if soldiers were met with violence, there could be casualties among the activists on board.

The warning, delivered by a senior military officer at a briefing with foreign journalists, was part of a diplomatic and media campaign that, along with publicized navy preparations, appears intended to head off the attempt to challenge the blockade.

Turkish Foreign Minister Ahmet Davutoglu said this month that the flotilla should be delayed until the impact of Egypt’s recent opening of a border crossing with Gaza became clearer.

An Israeli naval commando raid on a similar flotilla in May 2010 led to the death of nine people aboard a Turkish vessel carrying activists. The raid drew international condemnation, which in turn forced Israel to ease its land blockade of Gaza.

The high-ranking Israeli officer, speaking on the condition of anonymity under ground rules set by the military, said the navy was determined to enforce what he called a “maritime security blockade.” He said the blockade is aimed at stopping arms transfers to Gaza and had “nothing to do with humanitarian supplies.”

The officer said that militants in Gaza, which is controlled by the Islamist group Hamas, were arming themselves with rockets to attack Israel. The sea, he said, was their biggest potential supply route.

“We cannot and will not let any ship get into Gaza,” the officer said. He asserted that although the flotilla was not expected to be carrying weapons, allowing any breach of the blockade could open the door to such shipments in the future.

“A maritime security blockade is legal only if it is effective and complete,” the officer said. “You cannot have a selective blockade.”

The officer said the navy is training to intercept the flotilla ships using non­lethal means and avoiding close-quarters contact between troops and activists, which could result in casualties. Video footage of a navy drill made available by the military showed water cannons trained on ships simulating flotilla vessels.

The officer said, however, that “if there is violence that puts our soldiers’ lives in danger, we will have to respond, and there may be injuries and casualties.”

In last year’s raid, Israel said its commandos opened fire because they were attacked by activists when they rappelled onto the ship from helicopters.

In a public signal to the organizers of this month’s flotilla, the deputy commander of the Israeli navy, Rear Adm. Rani Ben-Yehuda, went before television cameras Thursday and invited the activists to dock in the Israeli port of Ashdod so that their cargo could be transferred by land to Gaza.

A similar offer last year was rejected by flotilla organizers, who asserted that their aim was to breach the naval blockade and bring supplies to Gaza free of Israeli controls.