JERUSALEM, SEPT. 9 -- A group of pro-Palestinian human rights activists from the United States today released a report alleging "widespread, frequent and pervasive" arrests and beatings of Arab children in the Israeli-occupied West Bank and Gaza Strip.

Israeli military officials and some Israeli journalists challenged the report's methodology and the qualifications of its authors. But its basic conclusion -- that detained Palestinian children are subjected to the same ill-treatment allegedly meted out to adults upon arrest -- is expected to fuel the controversy here over methods of interrogation used by the Shin Bet, Israel's internal security service.

In recent months the Shin Bet has been shaken by allegations that its interrogators routinely mistreat and occasionally torture people to extract confessions and information, then lie about those methods in court. These charges are the subject of an official commission of inquiry.

U.S. Ambassador Thomas Pickering voiced "strong condemnation" in a speech in May of what he called the "harsh treatment and measures used by the Israeli government against the people of the West Bank and Gaza." Diplomatic sources said Pickering has written a letter to the group that produced today's report, saying the embassy would pursue its allegations.

The group said its conclusions were based on first-person accounts by 16 Palestinian youths interviewed last spring at four locations. Three more males, ages 15 and 16, all of whom said they had served sentences for stone-throwing, charged at today's press conference that they had been beaten by soldiers and Shin Bet agents at two military prisons, Al Faraa, near the West Bank city of Nablus, and Ansar II in Gaza.

The Shin Bet does not comment publicly. But an Israeli military spokesman denied that detained youths were physically abused. "The use of violent means in the course of an investigation is strictly forbidden," the official said. "All complaints have been investigated and future ones will be also."

The official said that some youths between the ages of 12 and 14 may have been detained for "serious terrorist activity" such as throwing molotov cocktails or setting off explosives, but not for throwing stones. Those over 14 are treated similarly to adults, the official said.

Israeli soldiers in the refugee camps periodically round up youths suspected of throwing stones at military patrols and at civilian vehicles. Sometimes the roundups occur at schools during classes. Many youths are released after a few hours, but others may be held for days and some later face charges stemming from incidents of violence.

"The modus operandi of Israeli military rule dictates that every child, whether held for two hours in detention or sentenced to two months in prison, is subjected to systematic intimidation, humiliation and excessive physical abuse," the report charged.

It gave accounts of alleged beatings of some of these youths. Some said they were kicked, others said they were beaten on their genitals and several said they were hooded and made to stand for long periods without food or drink.

The report said those arrested often were prevented from seeing or contacting families, attorneys or the International Red Cross.

The authors of the report are Dinah Lawrence, a cultural anthropologist who has been active in Palestinian causes; Kameel Nasr, her husband, a Palestinian American who recently worked for Al Fajr, an Arabic daily here considered sympathetic to the Palestine Liberation Organization, and Karen White, a free-lance journalist who does volunteer work with the Christ Evangelical Episcopal Church in Nazareth.