The Israeli navy is said to have intercepted an Irish-owned aid ship bound for Gaza.
Initial reports suggested it had seized the Rachel Corrie some 55 kilometres west of the Palestinian territory. Activists then said the ship had not been boarded but that Israeli warships were following it.
Israel says it has not yet made contact with the ship. Nobel peace laueate Mairead Maguire is among its passengers.
While maintaining it won’t let the Rachel Corrie through, Israel says it will accept the ship’s cargo at its port of Ashdod, for onward land delivery to Gaza.
It comes five days after an Israeli naval operation in which nine Turkish activists were killed on another ship trying to break the blockade of Gaza. That raid triggered an international outcry.