RAMALLAH, WEST BANK — Tension between Palestinian factions exploded in their worst violence in nearly two years as a paramilitary police raid Sunday in the West Bank left six people dead. The clash underscored the risks for the Palestinian Authority as it moves forcefully, with fresh encouragement from President Obama, to disarm militants intent on attacking Israel.
Hamas, the Islamic group that governs the Gaza Strip, said the clampdown on one of its armed cells would bring "tough and harsh reprisal" against the U.S.-backed administration in the West Bank. The warning by Hamas spokesman Abu Obeida indicated that the group's tactic of lying low and passively weathering police sweeps in the West Bank was over.
An aggressive Hamas response, if sustained, would test Palestinian Authority President Mahmoud Abbas' hold on power and further complicate prospects for Middle East peace. The Israeli-Palestinian talks Obama is trying to revive had already been hurt by Hamas' victory in the 2006 parliamentary elections, its refusal to renounce violence against Israel and its armed expulsion of Abbas' secular Fatah forces from Gaza in June 2007.
The weekend clash was the deadliest between the Palestinian rivals since then. It began late Saturday when police in Kalkilya, a northern West Bank town with an elected Hamas mayor, spotted armed members of a Hamas cell they had been tracking for weeks. The police followed them to a two-story house stocked with automatic rifles and grenades and demanded their surrender.
Hussein Sheikh, an official in Abbas' Cabinet, said an eight-hour battle ensued, with 30 grenades and hundreds of rounds of ammunition fired from the house. It ended at dawn when police and paramilitary reinforcements from Abbas' Presidential Guard, National Security force and Preventive Security Service stormed the house.
Mohammed Samman, a leader of Hamas' military wing, and his assistant, Mohammed Yassin, were killed, along with a Hamas supporter who owned the house and three Palestinian policemen.
Hamas mobilized thousands of demonstrators Sunday in Gaza to protest the raid, accusing Abbas of collaborating with Israel to betray Palestinians who resist occupation by the Jewish state.
Israeli officials declined to comment on the raid or their degree of involvement. Samman and Yassin had been wanted by Israel for six years. The scores of Palestinian reinforcements could not have reached Kalkilya from other parts of the West Bank during the night without clearance though Israeli checkpoints.
Sheikh, the Cabinet official who serves as Abbas' day-to-day liaison with Israel, said the raid had not been coordinated with Israeli officials. He called it "a 100% Palestinian operation" aimed at disarming unauthorized militias and squelching illegal challenges to Abbas' administration.
The operation came two days after Abbas visited the White House to meet with Obama and renewed a pledge to rein in militants. Obama commended Abbas for "great progress in terms of security in the West Bank" under a U.S.-supervised program to train elite Palestinian Authority security battalions to police areas under its control.
Some graduates of the Jordan-based program were involved in the Kalkilya operation.
Israeli officials have also praised the program for reducing lawlessness in cities under Palestinian authority. But Prime Minister Benjamin Netanyahu has been reluctant to take the reciprocal step Obama again demanded publicly last week: a complete halt to the growth of Jewish settlements in the West Bank, which Israel seized in the 1967 Middle East War. Abbas, in turn, has refused to resume negotiations with Netanyahu's right-leaning government.
Western officials worry that the deadlock can only benefit Hamas. But Israeli officials say a withdrawal of their troops and settlers from the West Bank would turn the territory into a base for Hamas rocket attacks, as Gaza became after Israel's pullout in 2005. They contend that Abbas' security forces are still too weak to withstand an armed challenge by Hamas on their own.
Nonetheless, Abbas' forces have clamped down on Hamas in the last two years, arresting hundreds of militants.
The Kalkilya raid stemmed from a fire caused by an electrical short circuit in a mosque in the same neighborhood on April 9. As civil defense forces were dousing the flames, they stumbled upon what police called a Hamas weapons laboratory in the basement.
A search turned up 37 pounds of explosives and led to eight arrests. The mosque's blind imam was absolved of any responsibility and allowed to continue services there, Palestinian officials said, but the investigation put police on the trail of Samman and Yassin, the militants killed Sunday.
During the standoff, relatives of both men were brought to the house in an effort to talk them into surrendering.
"We wanted to arrest them without bloodshed, but they opened fire," said Sheikh, the Cabinet official.
However, the Palestinian Center for Human Rights, an independent organization, said security forces surrounding the house came under fire only after Yassin stepped outside to ask them to back off and was shot dead.
Kalkilya was reported tense Sunday and put under curfew after the policemen's funeral. Authorities took the Hamas militants' bodies to a morgue in another town, fearing that a public burial would turn into an unruly protest against the Palestinian Authority.
"I am sorry and sad for what happened, but I would not apologize to anyone for it," Palestinian Authority Prime Minister Salam Fayyad said during a visit to the city. "Our forces carried out their national duty to restore law and order."
Special correspondents Maher Abukhater in Ramallah and Rushdi abu Alouf in Gaza City contributed to this report.