Jerusalem (dpa) - The air campaign against Gaza in only the first of several phases of Israel's offensive in the strip, caretaker Israeli Prime Minister Ehud Olmert said Monday.

A "series of phases" was approved by the Israeli security cabinet last week, Olmert said in Jerusalem as he briefed Israeli President Shimon Peres on the offensive, a statement from Peres' office said.

Israeli Defence Minister Ehud Barak earlier said the offensive's goals were not only to curb rocket attacks from Gaza into southern Israel, but also to deliver a "harsh blow to Hamas."

"The operation continues and it will be deepened and widened for as much as is necessary in order to achieve the goals that we have set for ourselves: To bring back quiet to the south and to deliver a harsh blow to Hamas, which will result in an end to the fire," he told reporters as he toured the southern Israeli coastal city of Ashkelon Tuesday.

"The IDF (Israel Defence Forces) is concentrating its forces in the area of the strip and I don't want to go into details about what is planned next, but we will act with the means at our disposal to achieve this quiet and calm."