Israeli troops left behind a swath of destruction Thursday after their biggest offensive in the Gaza Strip (search) in years, destroying a multi-story building, damaging scores of houses, uprooting hundreds of trees and pulverizing local infrastructure.

The operation began early Tuesday after Palestinian militants blew up an Israeli armored vehicle in the Gaza City (search) neighborhood of Zeitoun (search), killing six Israeli soldiers.

The army said it conducted house to house searches in the neighborhood in an attempt to recover soldiers' body parts, including a severed head displayed by militants shortly after the attack.

Troops withdrew early Thursday after the body parts were retrieved, the army said. It said the damage to the neighborhood resulted from Palestinian resistance and the impact of the explosion that destroyed the armored vehicle.

"As a result of that explosion there was a lot of collateral damage over a large area," said military spokeswoman Maj. Sharon Feingold. "Also, two Palestinians tried to attack our forces and when we shot at them, explosives they were carrying blew up."

Further damage was caused when troops blew up workshops manufacturing rockets that are targeted at Israelis, Feingold said.

Local residents said the destruction was often indiscriminate.

Fatima Doula counted more than 75 bullet holes in the walls of her two-story home. All the windows had been blown out. Doula said she and 13 members of her family had cowered in a bathroom during the 36-hour Israeli operation because heavy Israeli gun and shell fire made it impossible to venture out.

"Nothing can justify what they did to us," she said.

Most of Zeitoun's damage was concentrated in a half-square-mile area along Salah al Din Street, the main thoroughfare. Army bulldozers dug up water mains and sewage pipes, flooding the area along a one-mile stretch and rendering the street impassable.

Palestinian Housing Minister Abdel Rahman Hamad said it would take at least three days to evaluate the extent of the damage. "This is total destruction aimed to make our people kneel down," he said. "It is an act of terrorism."

On either side of Salah al Din Street, scores of shops and dwellings shops were damaged, and hundreds of olive trees in neighboring groves were uprooted.

Salman Haji, 55, the owner of two seven-story buildings in Zeitoun, said the army had blown up one, reducing it to rubble, and damaged the other to the point where it would have to be pulled down.

It was not immediately clear why the army targeted Haji's buildings.

Haji said after the Israeli armored vehicle was destroyed, "the sky started raining with bullets" and an Israeli tank and Apache helicopter targeted his own buildings with shells and missiles.