At least three Israeli military ships surrounded a French-flagged yacht as it neared Gaza, seeking to breach Israel's blockade on the territory, an organiser told AFP on Tuesday.

"The boat is surrounded by at least three Israeli ships and since 9:06 am (0706 GMT) all the communications have been jammed. We can't get in touch with them by phone or by Internet," Julien Rivoire said by phone from Paris.

The boat set sail for Gaza after a night anchored at sea, despite Israeli warnings that it would intercept the vessel -- the only boat remaining from a flotilla of 10 ships that had planned to breach Israel's blockade this summer.

The Dignite/Al Karama set sail on Saturday from the Greek island of Kastellorizo following a troubled stay in Greece, after Athens imposed a ban on the departure of any ships involved in the flotilla.

On Monday, Israeli deputy foreign minister Danny Ayalon said the Jewish state would prevent any attempt to breach the naval blockade on Gaza.

"If this boat is on its way to Gaza, which is a breach of international maritime law, and tries a provocative act -- yes, we shall intercept it," he told reporters in Jerusalem.

"But I assure you we shall try our best to make those on board very comfortable."