The Israeli army killed nine fighters in and around the Gaza Strip on Saturday, and two more were killed by Israeli rockets on Sunday, raising the Palestinian death toll to 49 in one of the biggest and bloodiest offensives in four years of conflict.

Nearly 200 tanks and armored vehicles seized control of about 31/2 square miles of the coastal territory in a massive operation, witnesses said. The attack was launched after a Hamas rocket attack killed two Israeli toddlers in a border town on Wednesday.

Israeli Prime Minister Ariel Sharon and his security cabinet ordered the army to carve out a buffer zone to halt the rocket strikes that have fueled criticism of his plan to withdraw Jewish settlers from Gaza by the end of 2005.

The Israeli incursion, code-named Days of Reckoning, has focused on Jabalya, Gaza's largest refugee camp and a base for Hamas militants who fire daily barrages of makeshift Qassam rockets into southern Israel.

Shooting was sporadic in Jabalya's cramped alleys Saturday after fierce battles the day before. Witnesses and medics said an airstrike killed three Islamic Jihad radicals and a missile attack killed two Hamas fighters in Gaza City.

Four fighters were killed after crossing the border fence to try to infiltrate an Israeli community.

The Palestinian dead in the recent days' fighting include civilians as well as fighters. Israeli fatalities include two soldiers and a female jogger.

Israeli troops in one district of densely populated Jabalya used loudspeakers to urge dozens of Palestinians to leave their houses. Several families fled in fear that their homes would be demolished.

Soldiers, making their way through booby-trapped streets, have destroyed many houses since the beginning of the raid. The army says fighters use houses as cover for rocket attacks. Palestinians call the demolitions collective punishment.

The Palestinian leader, Yasser Arafat, condemned the Israeli incursion, saying: "I appeal to the world to . . . stop these inhumane and racist crimes."

Cutting short a visit to Jordan, Palestinian Prime Minister Ahmed Qureia also pointed the finger at Israel, but signaled his cabinet's consensus that rocket attacks should stop because they give the Jewish state what it sees as a pretext for more raids. "We appeal to all Palestinian factions . . . to seriously consider the higher national interest," Qureia told reporters.

The Arab League condemned the offensive.

The cycle of bloodshed has sent Sharon scrambling to counter critics who say his plan to pull out of Gaza has emboldened radicals trying to give the impression that Israel is being driven out. Israel is determined to smash armed groups before leaving.

A White House spokesman said that Israel "has the right to defend itself," but urged both sides to promote a U.S.-backed peace plan known as the "road map," which has been stalled by months of violence.