UNITED NATIONS, June 18 (Reuters) - Israel told the United Nations on Friday it reserved its right to use all necessary means to stop ships that it said planned to try to sail from Lebanon to bring aid to Gaza, blockaded by the Jewish state.

In a letter to U.N. Secretary-General Ban Ki-moon and to the Security Council, Israeli Ambassador Gabriela Shalev also called on the Lebanese government to prevent the ships from leaving.

An international furor erupted after the Israeli navy stormed a six-ship aid flotilla heading for Gaza on May 31, killing eight Turks and a Turkish-American on board. Israel said its commandos acted in self-defense after being attacked.

Following the outcry, Israel said on Thursday it was easing its land blockade of the Gaza Strip, which for the past three years has been controlled by Palestinian Hamas militants. But it said the sea blockade would continue.

Shalev said it appeared a small number of ships planned to sail from Lebanon and that while the organizers said they wished to take aid to Gaza, the true nature of their actions remains dubious.

Organizers had said they wished to become martyrs and there was a possible link to the Lebanese militant group Hezbollah, whose leader Hassan Nasrallah had called on Lebanese citizens to take part in such flotillas, Shalev said.

As a result, Israel cannot exclude the possibility that terrorists or arms will be smuggled onboard the ships in question, the Israeli envoy wrote.

Given the conflict between Israel and Hamas and the state of hostility between Lebanon and the Jewish state, Israel reserves its right under international law to use all necessary means to prevent these ships from violating the existing naval blockade imposed on the Gaza Strip, she said.

There were appropriate mechanisms for sending aid to Gaza, Shalev said, calling on Lebanon to demonstrate responsibility and to prevent these boats from departing to the Gaza Strip.

She also called on the international community to use its influence to stop the boats departing and to discourage their nationals from taking part in the action. (Reporting by Patrick Worsnip; Editing by Xavier Briand)