The aircraft flew at low altitude over the coastal area of Bayyada before turning inland toward the southern border regions of Hasbaya, Marjayoun, the Western Bekaa and Iqlim al-Tuffah, they said.

The four rounds had been fired from the region of Bayyada at 5:00 amon Monday in the direction of the Jewish state, the security sources said.

Three rounds landed inside Lebanese border territory and the fourth in the Mediterranean, they said.

In Jerusalem, the Israeli military said the mortar rounds had been aimed at an Israeli naval ship in territorial waters and caused neither casualties nor damage.

"It was a provocation by the terrorist organisations which operate from Lebanon under the protection of Syria and put our citizens and forces in peril," said Captain Sharon Feingold.

"We continue to hold the Lebanese and Syrian governments responsible for these operations which take place under their protection."

The Israeli military did not confirm a report on Israeli public radio which said the rounds were fired by the Lebanese Shiite Muslim fundamentalist Hezbollah.

A Hezbollah spokesman in Beirut did not wish to comment.

Hezbollah, which was instrumental in ending Israel's military occupation of southern Lebanon in May 2000, says it will maintain its campaign until the Shebaa Farms border area is also evacuated by Israeli troops.

On March 24, the radical Palestinian group -- the Popular Front for the Liberation of Palestine-General Command (PFLP-GC) -- said Israeli warplanes killed two of its fighters in southern Lebanon after they had fired a salvo of rockets into northern Israel.

WAR.WIRE