JERUSALEM - Taking aim from a hilltop, a sniper killed 10 soldiers and civilians at a checkpoint yesterday in the deadliest of a two-day string of Palestinian attacks that killed 21 Israelis.

Israel sent tanks and helicopters on retaliatory raids that hit several Palestinian Authority security targets, killing four Palestinian policemen, while Prime Minister Ariel Sharon and his Cabinet weighed additional military action.

Recent days have seen some of the worst carnage in months, and bitter comments by both sides pointed to further confrontations.

"There is no alternative but to put an end to Arafat's rule," Israeli Cabinet Minister Dan Naveh said in remarks that are expressed with increasing frequency in Israel.

The Al Aqsa Martyrs Brigade, a militia linked to Palestinian leader Yasser Arafat's Fatah movement, claimed responsibility for three of the four lethal attacks carried out in a 12-hour period from Saturday night to yesterday morning, including the checkpoint shooting.

Militants had vowed to strike after Israeli forces pushed into two Palestinian refugee camps in the West Bank last Thursday in search of militants believed responsible for earlier violence. During the incursions, 23 Palestinians were killed in three days, including gunmen, policemen and civilians.

"The Palestinian leadership considers the recent Israeli escalation ... to be aimed at destroying peace and security in the whole region," the Palestinian Authority said in a statement.

The shooting yesterday morning occurred at the military roadblock near the Palestinian village of Silwad. The army described it as an ambush carried out by a single sniper.

The gunman had a clear view from a hill overlooking the checkpoint. After the first Israeli was struck by gunfire, soldiers began climbing the steep hill toward the gunman and more were hit, witnesses said.

An army helicopter soon reached the area, but the assailant had escaped, said Hezi Tsur, a paramedic at the scene.

The dead included seven soldiers and three civilians. Six people were injured, the army and rescue services said.

The Al Aqsa Martyrs Brigades circulated a leaflet saying the shooting was in response to Israeli army actions in the two refugee camps.

In the Gaza Strip, Palestinian gunmen opened fire on a group of soldiers early yesterday along a road that runs on the Israeli side of the fence between the Gaza Strip and southern Israel.

One soldier was killed and four soldiers were wounded, the army said. The military wing of the radical group Islamic Jihad claimed responsibility for that attack in a telephone call to The Associated Press.

The pair of attacks yesterday morning followed a suicide bombing by a member of the Al Aqsa Martyrs Brigade Saturday night in a crowded ultra-Orthodox Jewish neighborhood of Jerusalem. The bombing killed nine Israelis and wounded dozens.

The dead included two babies, one seven months and the other 18 months, and children ages 3, 7, 12 and 15.

"I searched the streets like a mad person, street by street - it was crowded with people and I just screamed and screamed," said Aviva Nachmani, who eventually found her three children unharmed.

The Al Aqsa Martyrs Brigade also said it shot dead an Israeli police detective riding a motorcycle Saturday night along a desert trail in the West Bank, near Jerusalem.

Israel says Arafat bears responsibility for the Al Aqsa Martyrs Brigade and could halt their attacks if he was serious about ending the Palestinian violence.

Palestinian leaders denounced the suicide bombing and again said they oppose violence against civilians. But they say they cannot tell Palestinians to put down their weapons at a time when the Israeli military is regularly operating in Palestinian areas.

In retaliatory action yesterday, Israeli tanks shelled a Palestinian intelligence office south of Nablus, and the Palestinians said a policeman was killed.

Palestinians also reported a policeman killed when Israeli forces shelled a police installation outside Ramallah in the West Bank. Clouds of smoke billowed into the air, and one man was helped into a car, his face covered with blood.

Two more policemen died when Israeli troops fired on a police post in the West Bank town of Qalqiliya, the Palestinians said.

Meanwhile, the Israeli forces yesterday pulled out of the Balata refugee camp on the edge of Nablus, where troops had searched for militants and weapons since Thursday.

In the Jenin refugee camp, about 20 miles away, the Israeli forces pulled out Saturday, but sent at least eight tanks back into the camp on yesterday afternoon, camp residents said.