Israeli military forces arrested 30 suspected members of militant Palestinian groups Saturday in a series of raids in the West Bank, while thousands of Hamas supporters gathered in a hilltop cemetery here and vowed revenge for the killing of four fighters a day earlier by an Israeli missile strike.

The arrests in the cities of Hebron, Bethlehem and Nablus targeted members of Islamic Jihad and Hamas, known formally as the Islamic Resistance Movement, two groups that have stepped up attacks against Jewish settlements in Gaza and southern Israeli cities in recent days. Before dawn, Israeli attack helicopters buzzing over this city fired missiles into several automotive garages and machine shops that have sometimes been used to manufacture the rockets favored by the groups. No injuries were reported.

Hamas fired at least six rockets and more than 20 mortar rounds Saturday into the Negev region of southern Israel and several Jewish settlements inside Gaza that are scheduled to be evacuated next month. Israeli military officials reported light injuries but no fatalities.

A funeral procession made its way through Gaza City at midday bearing the coffins of four Hamas fighters killed a day earlier when the van they were traveling in was hit by an Israeli missile. Angry chants of "Revenge, revenge!" echoed in the streets and outside the graveyard where the men were buried. The green banners of Hamas, whipped by the wind, bobbed among the bleached headstones.

"This is our duty," said a 27-year-old teacher from Gaza who gave his name only as Abu Firas. Wiry, with a fringe of beard, Abu Firas said he had come to see the burial of Adel Haniyeh, who had been a classmate. Haniyeh's uncle, Ismail Haniyeh, one of the group's senior leaders, made his way between the graves surrounded by armed guards as freshly printed posters of his nephew posing with a rifle were distributed to the crowd.

"As long as Israel continues its aggression, we will continue our resistance," Abu Firas said.

The day provided more evidence that the informal truce declared in February by Israeli Prime Minister Ariel Sharon and Palestinian leader Mahmoud Abbas had fallen apart, at least for now. A Palestinian suicide bombing in the city of Netanya and a barrage of rocket attacks from Gaza have killed six Israelis in recent days. Israel has moved troops back into Tulkarm in the West Bank, and its forces have killed seven Hamas fighters and arrested dozens of others.

In a televised address from Gaza on Saturday evening, Abbas sharply criticized Israel's recent military operations but called on all Palestinian factions to reaffirm their commitment to the truce, saying, "We will not allow anyone to violate it.

"We hold the Israeli government fully responsible for the consequences of its policy, which reflects a step backward from what we had achieved," Abbas said. "No one could expect the continuation of the truce from one side."

The continuing violence comes as Sharon prepares to evacuate all 21 Jewish settlements in Gaza and four others from the northern West Bank, an operation that he has said would not be carried out amid Palestinian attacks.

Israeli tanks and infantry troops continued massing Saturday in several places near Gaza's northern border, although Israeli officials said it was unlikely those forces would enter the strip with the evacuation only weeks away. The withdrawal, known as disengagement, is scheduled to begin Aug. 15 and take several weeks to complete. Zalman Shoval, a Sharon adviser, said the troops were "ready to go, if need be."

"The more we approach the date of disengagement we shall see more and more attempts at terrorism," he said. "We expect the Palestinian Authority to do something about this. We don't think it will. So we will continue to act."

Israeli officials have said that Hamas and Islamic Jihad, movements that reject the 1993 Oslo accords with Israel and deny its right to exist, are trying to make the Israeli withdrawal from Gaza appear to be a response to the groups' attacks. Hamas officials have said the Israeli evacuation is in part a result of their armed attacks.

Of the 30 men arrested Saturday, the Israeli military said, 26 are Hamas members. The rest belong to Islamic Jihad.

Tensions between Abbas's ruling Fatah party and Hamas appear far from resolved. Palestinian security services and Hamas gunmen exchanged fire for hours here Friday after police moved against members of the Hamas military wing in an effort to halt rocket fire into Israel. In his address, Abbas called fighting Palestinian security forces a "crime that would not pass without punishment."

Yellow Fatah banners were absent from the blanket of green Hamas flags accompanying the funeral procession. A 21-year-old tailor in a Hamas baseball cap, who gave his name as Abu Mussab, said the Fatah-dominated Palestinian Authority "uses all of its force to stop Hamas when it should be using it to stop the Israelis."

"I hope we can reach a real agreement," he said, watching throngs of angry young men in green headbands, many of them brandishing assault rifles, gather for the burial. "We are not a faction that opposes the Palestinian Authority, only the Israelis."

An Israeli army officer speaks to troops at a staging area just outside the Gaza Strip after pre-dawn missile strikes in Gaza City. The helicopter strikes targeted suspected manufacturing sites for rockets favored by members of the militant Palestinian groups Hamas and Islamic Jihad in attacks against Jewish settlements in Gaza and southern Israeli cities in recent days. No injuries were reported.Palestinians in Gaza City carry coffins holding the bodies of Hamas members killed in an Israeli airstrike Friday as an informal truce continued to unravel.