Israeli troops swept into a Palestinian town in the Gaza Strip before dawn today, bulldozing houses and police outposts, killing two police officers and two youths and arresting suspected militants before withdrawing after darkness fell. 
A fifth Palestinian was killed today by Israeli troops in the southern Gaza Strip when he tried to enter a Jewish settlement to carry out a grenade attack, the army said.
Palestinians reported 13 people were killed and scores injured during two straight days of lightning raids by Israeli armored forces and infantry.
Israeli officials said the sweeps would continue as long as Yasser Arafat's Palestinian Authority refused to quash terrorist groups. Palestinians said the Israeli attacks, which have targeted Arafat's police and security forces, have made it impossible to crack down on hard-line Islamic groups that have conducted terrorist attacks against Israelis.
As the violence surged, the State Department announced that U.S. envoy Anthony C. Zinni, who failed in nearly three weeks of mediation to nudge the two sides toward a cease-fire, would return to Washington for consultations.

Although it was expected, the decision to suspend Zinni's mission was an acknowledgment that the Bush administration's first serious push to end the bloodshed between Israelis and Palestinians had reached a dead end, at least for the time being.
Zinni's 20 days in the region coincided with one of the worst eruptions of violence in nearly 15 months of fighting. Since the retired Marine Corps general arrived Nov. 26, several dozen Israelis have been killed in a string of Palestinian suicide bombings and other attacks, and almost as many Palestinians have died in Israeli reprisal raids.
The worst fighting today took place in Beit Hanoun, a town of about 20,000 people near the Gaza Strip's northern border with Israel. Israel described Beit Hanoun as a hotbed of Palestinian terrorism, and said militants there had fired mortars and rockets at nearby Jewish communities in Gaza and beyond the border fence inside Israel.
Israeli forces rumbled into the town in convoys of tanks and armored fighting vehicles. Witnesses said Palestinian youths threw stones at the advancing Israeli forces and set tires ablaze. Before long, the clashes escalated into gunfights between Palestinian security forces and Israeli troops.
Four Palestinians were killed by Israeli gunfire, including two police officers and two boys, ages 12 and 16, according to Shifa Hospital in nearby Gaza City. Fifty Palestinians were injured in today's fighting, the hospital said. The Israeli army said 15 Palestinians were arrested.
Palestinians said the Israelis bulldozed five houses, three security offices and a headquarters of Arafat's Fatah movement. One of the houses belonged to Salah Shahed, the founder of the armed wing of the militant group Hamas, but witnesses said he was not in the area at the time.
Israeli forces moved onto the grounds of the Beit Hanoun Secondary Girls' School, briefly putting up tents in the yard and raising an Israeli flag atop one building, witnesses said.
"We did not carry out this operation thinking it will put a complete stop to terror, but it definitely damaged the effectiveness," said Brig. Gen. Israel Ziv, the Israeli commander for Gaza. He said if the Palestinian Authority did not wage a concerted war against terrorism, "we will have no choice but to continue these operations."