Israeli tanks rolled into Gaza City Thursday morning for the first time since the start of the nearly 17-month-old Palestinian uprising and blew up a local radio station, witnesses said.

Loudspeakers at mosques called on Palestinians to confront the Israeli invaders, and police and gunmen raced to the scene.

Troops also killed four Palestinians and wounded 35 in the Rafah refugee camp near the Egyptian border in a morning raid, Palestinian doctors said. Another was killed at daybreak near the border, witnesses said.

In Ramallah, meanwhile, an Israeli helicopter fired at least one rocket at a building inside Palestinian leader Yasser Arafat's compound shortly before dawn. No casualties were reported.

The army confirmed the attacks and said they were part of a continued response to Palestinian violence. Residents said Israeli troops began pulling out of Gaza City after three hours.

Elsewhere in the region, a Palestinians attacker was killed Thursday after he and another Palestinian opened fire on Israeli soldiers manning a checkpoint in the northern West Bank, military officials said. The soldiers returned fire, killing one assailant immediately. Two soldiers were wounded.

The body of another man was found during a search of the area but it was not immediately clear if it was the second gunman or a bystander. Searches continued for another gunman, the army said.

The past week has been one of the bloodiest since Israeli-Palestinian fighting began in September 2000. Seventeen Israelis and at least 53 Palestinians have been killed.

After losing 13 soldiers during the bloody week, Israel is changing its military tactics to deal with what it views as a guerrilla war, a top Israeli official said.

In Wednesday's fighting, Israeli troops fired missiles, tank shells and machine guns at Palestinian Authority positions in reprisals for a Palestinian ambush that killed six Israeli soldiers. Also, Israeli soldiers killed two Palestinian militants who were about to fire rockets at Israel, according to media reports and Palestinian officials.

The Palestinian assault Tuesday night at an Israeli military checkpoint near the village of Ein Arik, west of Ramallah, sparked a debate on the wisdom of maintaining the scores of military roadblocks throughout the West Bank and Gaza. Prime Minister Ariel Sharon's spokesman, Raanan Gissin, said Israel would change strategy to focus on "small-scale counter-guerrilla, counter-terrorist operations."

After a meeting of top ministers, Sharon announced a "different course of action." He gave no details, but Gissin said Israel would reduce the number of large operations and in favor of smaller-scale actions "with the purpose of really trying to tip the terrorists off-balance."

That would include a continuation of the targeted killings of militants suspected of involvement in terrorism against Israelis, the spokesman said.

The Palestinians might be changing their tactics as well. Several Palestinians close to the militant groups said the checkpoint assault reflected a new focus: targeting Israel's occupation in the West Bank and Gaza as opposed to attacks within Israel itself.

The Palestinians said on condition of anonymity that the aim is to focus attention on the lands Palestinians claim for a state and rally world support.

Both sides buried their dead on Wednesday. Thousands of angry Palestinians marched behind coffins throughout the Palestinian areas, pledging revenge, while weeping Israelis buried their soldiers amid calls for new, harsher measures to stop the violence.

Meanwhile, Palestinians asked for an urgent U.N. Security Council meeting, moving to hold Israel accountable for what they said was a "crisis situation." Diplomats said consultations could be held Thursday morning in New York.

Arafat has been trapped in his West Bank headquarters in the town of Ramallah, surrounded by Israeli tanks, for more than two months. Gissin said Israel will not target him but suggested it might stop the stream of foreign diplomats going to meet him there.

Sharon said that Israeli pressure on Arafat is meant to speed his replacement by other leaders. "The heavier the pressure will be, the shorter will be the time when we will perhaps have someone else to negotiate," Sharon told U.S. Jewish leaders.

Arafat appeared unimpressed.

"Neither tanks nor planes can scare us, they won't prevent us from achieving our demands," said the Palestinian leader.

Israelis, meanwhile, struggled to understand how six of their soldiers had been so easily killed, apparently by four attackers who got away.

West Bank army commander Brig. Gen. Gershon Yitzhak said the attackers took advantage of an open crossing point for Palestinian workers moving between different parts of the West Bank. He said they suddenly opened fire on soldiers at the checkpoint, killing three.

They then shot and killed the platoon commander, who was in the courtyard of a nearby army enclave, before entering a trailer in the enclave where three more soldiers were sleeping. Two of those soldiers were killed and a third seriously wounded.

Military commentator Alex Fishman wrote in the Yediot Ahronot daily that the soldiers at the checkpoints are "sitting ducks."

There are scores of Israeli roadblocks scattered throughout the West Bank aimed at limiting movement of militants. Critics say they fan the flames of hatred by making life a misery for masses of ordinary Palestinians, and are not effective against militants.

Undeterred by the retaliation, Palestinians vowed to keep up the fight.

"Israeli civilians will not be safe as long as our people are not safe," said Nasser Awais, a leader of the Al Aqsa Brigades, a militia associated with Arafat's Fatah group and which claimed responsibility for the roadblock assault.

Since violence erupted in September 2000, at least 986 people have been killed on the Palestinian side and 281 on the Israeli side.

The Associated Press contributed to this report.