GAZA CITY Ñ Palestinian insurgency groups, echoing Hizbullah tactics, have conducted a major multi-stage attack against Israel's military along the Egyptian border.

At least five Israeli soldiers were killed and another six were wounded in the Palestinian strike in the southern Gaza Strip on Sunday. An Israeli military outpost was rocked by two huge bombs that destroyed a tunnel that was dug underneath the military position.

"This was one of the most sophisticated attacks ever by the Palestinians," a Palestinian source said.

Hamas and the ruling Fatah movement claimed joint responsibility for the attack, Middle East Newsline reported. A communique said the two groups used 1.5 tons of explosives in the attack against an Israeli installation.

It was one of the first successful multi-stage attacks by Palestinian insurgency groups since 2001. Palestinian sources said the insurgents first detonated two bombs that destroyed the Israeli military outpost, then attacked reinforcements with mortars, anti-tank missiles and automatic fire.

At the same time, a Hamas operative sought to place a mine along the Egyptian-Gaza border. The attempt was said to have been foiled by Israeli troops.

This was the second major tunnel bombing by Palestinian insurgency groups in 2004. In August, Israel's military closed the Rafah border terminal with Egypt because of an alert that Palestinian insurgency groups were constructing a tunnel for a major attack on an Israeli military target.

The Hamas-Fatah communique said two Palestinian suicide bombers were used in the attack, reported to have been planned in August 2004. The announcement said the two groups constructed a 600 meter tunnel that extended from farmland outside Rafah to the Israeli outpost along the Egyptian border.

Israeli Home Front units dug through the rubble in the search for soldiers. The soldiers operated in the night as Palestinian snipers maintained fire.

Israeli military sources said Hamas and Fatah have been trained by Hizbullah to carry out multi-stage attacks. Hours before the explosion, Hamas fired five Kassam missiles toward an Israeli community in the northern Gaza Strip. Nobody was injured.

On Monday, Israeli troops killed a Hamas leader in the West Bank city of Nablus.

Israel's military was not expected to launch a major retaliatory strike, the Israeli sources said. They cited U.S. opposition to any major military operation amid efforts to hold elections on Jan. 9 for a Palestinian leadership.