RAMALLAH, West Bank -- An Israeli helicopter fired missiles at a car Saturday, killing five Palestinians including a militant and two children, witnesses said. Elsewhere in the West Bank, a Palestinian gunman infiltrated a Jewish settlement, wounding two people before he was killed.

Also Saturday, Israeli soldiers arrested the top West Bank political leader of the Islamic militant group Hamas during a sweep in the city of Ramallah. And late in the day, an Israeli tank fired a shell into a house in a Gaza Strip refugee camp, moderately wounding five members of a family, Palestinian hospital sources said.

The militant Popular Front for the Liberation of Palestine claimed responsibility for the attack.

It was the first Palestinian attack to bring Israeli civlian casualties since an Aug. 4 suicide bombing killed nine.

Israel has pursued an intense crackdown on militants while imposing curfews and restrictions on Palestinians in West Bank towns and areas under the military's control. A million Palestinian children began a new academic year Saturday, braving curfews, roadblocks and closures to get to their schools.

An Israeli helicopter fired three missiles at a car in the northern West Bank town of Toubas, apparently targeting two militants from the Al-Aqsa Brigades, affiliated with Yasser Arafat's Fatah movement.

One of the militants was killed, as were two teens in the car and a 10-year-old boy and a 6-year-old girl walking nearby, said witnesses and hospital officials. The other militant and six bystanders were wounded.

Palestinian Cabinet minister Saeb Erekat called the strike a "brutal act of murder."

The Israeli army issued a statement expressing "sorrow over the loss of civilian life." It said its helicopters "hit a car carrying several wanted men responsible" for planning attacks in Israel that were to have taken place in the next few days.

In Ramallah, the Hamas leader, Hasan Yousef, was captured at a house in the center of town and herded blindfolded into an Israeli military vehicle along with another unidentified man.

Yousef heads the political wing of Hamas in the West Bank, and the Israeli army said it had been hunting for him for some time.

Hamas has claimed responsibility for scores of suicide bombings that have killed hundreds of Israelis in the near two-year conflict.

In the Gaza Strip late Saturday, some 5,000 people took to the streets to protest Yousef's arrest and the helicopter strike at Toubas. The crowd chanted calls for revenge and housed Palestinian flags and Hamas banners.

In other violence, the Al-Aqsa Brigades on Saturday executed Mohammed Abu Oun, 29, in the center of the northern West Bank village of Jabaa, after accusing him of helping the Israelis kill a local militant leader in early August, according to local residents.

Israel says its crackdown in the West Bank and Gaza is necessary to root out militants in the wake of a spate of suicide bombings inside Israel -- though there's been a lull in such bombings for almost a month.

Palestinians say Israel's actions constitute collective punishment that has decimated their lives.

On Saturday, tens of thousands of Palestinian children in their school uniforms tried to make their way to their schools. Some lined up outside checkpoints, opening their backpacks for Israeli soldiers to check. Others took dirt side roads or mountain paths to avoid the roadblocks.

Israel lifted its curfew for part of the day in several West Bank towns, though it remained in place in Jenin and the Israeli-controlled section of Hebron, keeping thousands of students at home.

Also Saturday, Interior Minister Abdel Razak Yehiyeh, who heads the Palestinian security forces, met U.S. Deputy Assistant Secretary of State David Satterfield as part of talks aimed at reducing tensions.