Reporting from Ramallah, West Bank, and Jerusalem — Israel's week-old assault on the Gaza Strip has widened the rift between Palestinians who back the search by moderate leaders for a peace accord with the Jewish state and those drawn to Hamas' call for armed struggle.

The breach was on display Friday in the West Bank as the territory's U.S.-backed Palestinian Authority leadership, striving to contain rising anger over the death toll in Hamas-ruled Gaza, sent police to put down pro-Hamas demonstrations.

Thousands enraged by the bloodshed have joined protests in West Bank cities. One in Ramallah after Friday prayers turned into a shouting match between about 2,000 marchers with green Hamas flags and 500 others with the yellow banners of Palestinian Authority President Mahmoud Abbas' Fatah movement.

Though condemning the assault as "criminal," Abbas has insisted that Hamas is responsible because it ended a truce with Israel two weeks ago. Hamas, in turn, has branded him an Israeli collaborator.

The two factions shared power, uneasily, in an elected government until the militant Islamic group ousted Fatah's secular forces from Gaza in June 2007. Their violent split left the Palestinian Authority in charge of only the West Bank, and the divide has deepened since.

Investment spurred by hopes for peace with Israel has trickled into the West Bank, lifting its economy. Gaza has slid deeper into poverty, punished for Hamas' belligerence by an Israeli blockade that severely restricts supplies of food, fuel and other essentials to the enclave's 1.5 million people.

As Hamas stepped up rocket attacks against Israel from Gaza in the last year, Abbas has pursued talks with Israeli leaders, brokered by the Bush administration, with the aim of establishing an independent Palestinian state. U.S. officials hoped the process would boost Abbas' stature and weaken Hamas' message of armed resistance.

But after 14 months, Israeli leaders and Abbas are no closer to an accord and Hamas remains entrenched in Gaza.

Each faction now views the Israeli offensive as an opportunity to gain at the other's expense. Fatah officials have sent messages of hope to their supporters in Gaza that Hamas will be driven from power.

Hamas' top political leader, Khaled Meshaal, has called for an uprising in the West Bank, "a peaceful one against the Palestinian Authority and a military one against Israel."

The potential for rebellion in the West Bank, however, is limited. The Israeli army patrols the territory heavily, and Abbas' security forces, built up with Israel's blessing, have arrested dozens of Hamas activists in recent months.

In addition, Palestinians say they are reluctant to rally behind any national cause not backed by all political factions.

"People are frustrated by this internal division," said Hani Masri, a political analyst in Ramallah. "They see each faction working alone, for itself, unable to bring about any improvement for the Palestinians as a whole."

That disillusionment, he said, helps explain why unrest over the violence in Gaza has been less intense in the West Bank than in some Arab capitals.

The bloodshed has nonetheless threatened to undermine Abbas' authority. As the elected president of all Palestinians, the 73-year-old Abbas has demanded a halt to the airstrikes, which have claimed more than 400 lives in Gaza since they began last Saturday.

He sees peace talks with Israel as the central mission of his presidency. Yet after hours of face-to-face negotiations with Israeli leaders, he has achieved no apparent influence over what they do in Gaza and delivered little in the way of concessions to help persuade Gazans to turn against Hamas.

"The Israelis claim they are attacking Gaza to weaken Hamas, but in fact they are strengthening Hamas," said Mustafa Barghouti, an independent member of the Palestinian parliament who led Friday's march in Ramallah. "Mr. Abbas is perceived now as incapable of protecting all the Palestinian people."

Both Israel and Abbas' government worry about Hamas' considerable popular support in the West Bank and its potential to challenge Fatah's supremacy in the territory.

Fatah officials were alarmed on the first two days of the airstrikes when protesters brought Hamas banners into the streets of Hebron, Bethlehem and Ramallah, provoking clashes with Israeli troops. Palestinian police intervened in all three cities, wounding three protesters with gunfire in Hebron.

Fatah security officials denied that their men were cooperating with Israel to suppress pro-Hamas protests.

But Mouin Rabbani, an independent Middle East analyst based in Amman, Jordan, said the police action reinforced an impression that Abbas is too close to Israel and secretly supports the bombing of Gaza.

"People are looking at Israel's campaign in the Gaza Strip and Abbas' campaign in the West Bank as two sides of the same coin," he said.

Hamas stoked that suspicion with a statement accusing Abbas of having collaborated with Israel by planting a cell of Fatah spies in Gaza to pinpoint the hide-outs of Hamas leaders being targeted by Israel for assassination. Fatah officials denied the accusation.

In recent days, Fatah has set strict rules to avoid expressions of support for Hamas.

All political groups, including Hamas, have agreed to conduct protests against Israel under a single Palestinian flag.

That rule was observed at demonstrations in several cities during the week and at most of them Friday, when Hamas urged other groups to join in a "day of wrath" against the bombings.

But in Hebron and Ramallah, Friday's marches devolved into chaos when the green Hamas banners came out.

In Ramallah's Manara Square, a phalanx of Palestinian police officers, some in civilian clothes, emerged from the crowd and began pushing Hamas supporters along a side street. A few protesters pushed back and were arrested.

The Hamas crowd began chanting: "With our soul, with our blood, we will sacrifice for you, Gaza!"

Fatah supporters unfurled their flags and shouted back: "Unity! Unity!"

The rally spread to an Israeli checkpoint at the edge of the city, where dozens of youths set fires and threw stones at soldiers, who fired rubber bullets, sound grenades and tear gas.

As the crowd dispersed, two participants in the march voiced sharply diverging views about what it all meant.

"People are tired of Hamas and its politics and don't want the West Bank to become like Gaza," said Jamil Kasem, 39, of Ramallah. "Hamas is weak, but it is trying to create chaos in the street to make people believe it is stronger than Fatah."

Mohammed Midya, 45, a Hamas supporter who teaches math at Birzeit University in the West Bank, said people were more concerned about the bombing than about the Fatah-Hamas conflict.

"They see what's going on in Gaza," he said, "and it upsets them on a human level."