Israel intercepted a drone sent from Gaza on Monday as it flew just off the shore of the port city of Ashdod, about 14 miles north of the Palestinian enclave, adding a new element to a week-old conflict.

The military wing of Hamas claimed responsibility for sending a “number of drones” into Israel, describing the event on its website as one of the “surprises” it had promised over the last week and saying the drones had been dispatched on “special missions.” An Israeli military spokesman did not rule out that the possibility that the Palestinians had access to additional drones.