Aircraft also struck the Sheikh Radwan cemetery in Gaza City, destroying about 30 graves — some just recently dug — and scattering bits of flesh and body parts for yards (meters), residents said. The stench of scorched and rotting flesh hung over the area.

"There was flesh on the roofs, there was small bits of intestines. My neighbor found a hand of a woman who died a long time ago, we put it all into a plastic bag," said resident Ahmad Abu Jarbou. "One man who buried his cousin yesterday couldn't find the body at all."

Maj. Avital Leibovich, a military spokeswoman, said the army targeted a weapons cache next to the cemetery and a nearby rocket-launching site. She said the heavy damage was the result of secondary explosions.

Israel has repeatedly accused Hamas of using mosques, schools and other civilian areas to stage attacks or store weapons.

In other fighting, artillery units fired shells that spread white smoke above the city center, witnesses said. Human Rights Watch has accused Israel of using phosphorous shells — a weapon that can burn anything it touches. The Israeli military has denied reports that it has improperly used white phosphorous shells, saying only that it uses munitions is in accordance with international law.

The International Committee of the Red Cross urged Israel to exercise "extreme caution" in using the incendiary agent, which is used to illuminate targets at night or create a smoke screen for day attacks, said Peter Herby, the head of the organization's mines-arms unit. The ICRC said it had no evidence to suggest white phosphorous was being used improperly or illegally.

Fireballs and smoke plumes from Israeli bombing have become a common sight in the territory of 1.4 million people, who are trapped because Israel and Egypt have blockaded border crossings ever since the Islamic Hamas overran Gaza in June 2007.

Humanitarian concerns have increased amid the onslaught although some aid is getting through to Gaza during daily three-hour lulls Israel has allowed to let in supplies. A total of 111 truckloads of food and medical supplies were to pass through on Wednesday, the military said.