Israel Wednesday launched its first ground offensive in the Gaza Strip since leaving the territory last year, stepping up pressure on Palestinian militants to release an abducted soldier.

Tanks and infantry, backed by assault helicopters and artillery, set up a strategic observation post at a disused airport outside the southern town of Rafah as masked gunmen waited behind barricades and in alleyways for battle to begin.

Threatening "extreme steps" if Corporal Gilad Shalit was not freed, Israeli Prime Minister Ehud Olmert said the operation would continue "over the coming days."

Launching the offensive three days after Shalit was captured in Israel by gunmen in a cross-border raid, Israeli aircraft struck at three bridges in what the army said was an attempt to stop militants moving the captive.

A helicopter attack on Gaza's only power plant sent flames shooting into the sky and cut off electricity to much of the coastal territory, where 1.4 million Palestinians live. Engineers said repairs could take six months.

Palestinian President Mahmoud Abbas called the bombardment of civilian infrastructure "collective punishment and a crime against humanity."

Olmert said Israel had "no intention of recapturing" the Gaza Strip. "We have a central goal and that is to bring Gilad home," he said in a speech in Jerusalem.

Mushir al-Masri, a legislator from the governing Hamas movement, said Olmert's "adventurism" was "putting the missing soldier at risk."

Overflying Gaza, Israeli warplanes caused sonic booms that rattled Palestinian nerves and carried out what a military spokeswoman said were several missile strikes in open areas. Security sources said an explosion that killed two Palestinians at a home in the Gaza Strip Wednesday was accidental and not related to the Israeli offensive.

In another challenge to Israel, a militant group threatened to kill a Jewish settler it said it seized in the West Bank if the Gaza raid continued. Israeli authorities said the settler has been missing since Sunday.

Abu Abir, a spokesman for the Popular Resistance Committees, showed a photocopy of the missing settler's ID card at a Gaza news conference. Abu Abir and other militants left in a hurry at the sound of Israeli aircraft breaking the sound barrier.

(China Daily June 29, 2006)