Fearful that Hamas' momentum could spread to the West Bank, Fatah went on the offensive there, rounding up three dozen Hamas fighters. Angry militants threw office furniture out a third-story window of the Palestinian parliament building in Ramallah, then set fire to the office of three Hamas lawmakers.
A Hamas activist was shot and killed in Nablus, the first person to be killed in the West Bank after days of violence in Gaza; the Al Aqsa Martyrs' Brigades, a violent Fatah offshoot, claimed responsibility.
It was a day of major victories for Hamas and its backers in Iran and Syria — and of devastating setbacks for the Western-backed Fatah.
On TV, Hamas publicly humiliated its enemies, showing the capture of Fatah holdouts, reports CBS News correspondent Richard Roth.
In one particularly humiliating scene, masked Hamas fighters marched agents of the once-feared Preventive Security Service out of their headquarters, arms raised in the air, stripped to the waist and ducking at the sound of a gunshot.
What Hamas didn't broadcast were the brutal streetside executions, adds Roth.
Witnesses, Fatah officials and a doctor reported executions by Hamas militants of defeated Fatah fighters; Fatah said seven of its men were shot in the head, gangland-style. Hamas denied any such killings.
The violence has killed at least 90 people in the past five days, including 33 on Thursday alone.
Abbas, of Fatah, fired the Hamas Prime Minister Ismail Haniyeh and said he would install a new government, replacing the Hamas-Fatah coalition formed just three months ago. Abbas' decrees won't reverse the Hamas takeover of Gaza. Instead, his moves will enable Fatah to consolidate its control over the West Bank, likely paving the way for two separate Palestinian governments.
Haniyeh said that Abbas' decision to fire him and his government over Gaza violence was "hasty." Haniyeh told a late-night Gaza news conference that Abbas and his advisers did not consider "the consequences (of the decision) and its effects on the situation on the ground."
Because Fatah has recognized Israel's right to exist and signed on to past peace agreements, the international community's boycott of the Palestinian territories in the wake of Hamas' electoral successes may no longer apply to the West Bank, just to Gaza. Some 2 million Palestinians live in the West Bank, while 1.4 million reside in Gaza.
Hamas' success has thrown into turmoil everything from Mideast peacemaking to Palestinian statehood to relations with Israel and the West.
"The era of justice and Islamic rule has arrived," Hamas spokesman Islam Shahawan said.
Fatah's old demons — corruption, petty quarreling, lack of leadership — led to its dismal performance. While disciplined Hamas systematically hoarded weapons, Fatah's Gaza leader, Mohammed Dahlan, preferred travel and West Bank politics to preparing for the inevitable showdown with its rival. Dahlan returned Thursday from Egypt, where he stayed several weeks after knee surgery. But instead of going to Gaza, he headed for Ramallah.
In other developments: