An Israeli undercover arrest operation on Wednesday turned into a chaotic gun battle in the center of Ramallah, leaving 4 Palestinians dead and about 50 wounded.

It was the second time in two days that the Israeli military had raided Ramallah, the Palestinian political headquarters in the West Bank, to seize a Palestinian high on its most-wanted list. However, unlike the operation on Tuesday, which had led to the arrest of Ibrahim Hamed, a long-sought Hamas leader, and caused no casualties, the action on Wednesday quickly degenerated into a shootout around the main traffic circle in the congested city.

Palestinian leaders said the timing of the raid, while Prime Minister Ehud Olmert of Israel was visiting Washington, showed bad faith.

"Israel is trying its best to block any effort to calm the situation," said Nabil Abu Rudeineh, an aide to Mahmoud Abbas, the Palestinian Authority president.

The Israeli military described Muhammad Shubaki, the target of the raid on Wednesday, as a senior figure in Islamic Jihad, the group responsible for almost all of the suicide bombings against Israel in the past year.

An Israeli undercover unit, disguised as Palestinian civilians, seized Mr. Shubaki in a building on Manara Square in the center of Ramallah, Palestinian security officials said.

But word quickly spread that the Israeli forces were in the area, and youths began throwing rocks. A civilian car used by the Israelis was set ablaze, and gun battles broke out. Shortly afterward, uniformed Israeli soldiers in jeeps arrived, and the conflict escalated, the Israeli military and the Palestinian security forces said.

Four Palestinians, including one member of the Palestinian security forces, were killed, and about 50 Palestinians were injured, hospital officials in Ramallah said. One Israeli soldier was hit in the head by a rock, the Israeli military said.

The military reported that it had used rubber bullets, tear gas and live fire against the Palestinians, but that it had no information on Palestinian casualties.

The Israeli military has carried out arrest raids in the West Bank almost nightly for the past four years, and thousands of Palestinians accused of militant activity have been imprisoned.

However, it is highly unusual for a large contingent to enter the center of Ramallah during the day. The undercover unit presumably sought to slip in and out unnoticed, though the military declined to comment on the specifics of the operation.

In the Gaza Strip, a Palestinian security chief was killed Wednesday when his car blew up, Palestinian security officials said. The security chief, Nabil Hodhod, chief of the Preventive Security forces in central Gaza, was considered loyal to Mr. Abbas, The Associated Press reported.

No one claimed responsibility immediately, though rival Palestinian factions have been fighting almost daily in Gaza in the past few weeks. Most of the fighting has involved Hamas, the militant Islamic movement that leads the government, and Fatah, which Mr. Abbas leads.

In Khan Yunis, in southern Gaza, men shot three members of Hamas on Wednesday, killing one, Palestinian security officials said.

Hamas, Fatah and other Palestinian factions plan to open a "national dialogue" on Thursday to try to stop the infighting.

Copyright 2006 The New York Times Company