Israeli Prime Minister Ehud Olmert said on Tuesday that the bombardment of Hamas targets in Gaza so far was "the first of several stages" approved by the Jewish state's security cabinet.

The blitz that began on Saturday was "the first of several stages approved by the security cabinet," Olmert told President Shimon Peres in a briefing, according to the latter's spokesperson Ayelet Frisch.

Israel unleashed its deadly bombardment of Hamas targets in Gaza on Saturday in retaliation for persistent rocket fire from the territory.

Tanks, armoured vehicles and infantry forces were massing along Israel's border with Gaza on Tuesday, as the military said it was ready to launch a ground offensive in the densely populated territory if ordered to do so.

"The government is giving the military its full backing and the room for manoeuvre to achieve the goal set out by the government," Olmert was quoted as saying.

Peres said that "Israel is not fighting the Palestinian population but a terror organisation that is determined to continue the violence and destabilise the region."

The Israeli blitz has killed at least 360 Palestinians and wounded 1 690, according to medics. At least 57 of the dead have been civilians, according to the UN.

Gaza militants have fired more than 250 rockets into Israel since Saturday, killing four people — three civilians and one soldier — and wounding some two dozen more, according to medics.

AFP