Until this week, Fatah had calculated that its supremacy in the West Bank would serve to check attacks on its forces in Gaza. But Thursday there was no stopping Hamas here.
Pro-Fatah broadcasts went off the air and Fatah's Voice of Palestine radio studios were set ablaze. Hamas-controlled radio stations broadcast appeals to Fatah gunmen to "surrender or face merciless retribution."
Hamas' militia, the Izzidin al-Qassam Brigade, said it shot to death a captured Fatah militant, Samih Madhoun, one of 55 Fatah men on a widely circulated hit list, for having broadcast a pledge to kill all members of the Islamic movement.
Hamas spokesman Sami abu Zuhri said the movement's weeklong assault was a defensive move against a group within Fatah that was collaborating with Israel and the United States to sideline Hamas. He said Hamas wanted to bring all the Palestinian security forces under the control of the unity government formed in March.
Abbas denounced the Hamas offensive as an attempted coup. He decided to dissolve the Cabinet "to remove the shroud of legitimacy from a party that has acted in an illegitimate way," a person who spoke to him said.
He can name a new government for the duration of the state of emergency but cannot dissolve the Hamas-dominated parliament. He must get the legislative body's approval to extend the emergency beyond 30 days or to seat a new government after it is lifted.
Some experts said Abbas might be able to work around those restrictions because parliament lacks the quorum required for a vote; many Hamas lawmakers are in Israeli jails.
In Washington, Secretary of State Condoleezza Rice said the United States backed Abbas' decrees. He had informed Rice of his decision in a phone call.
"President Abbas has exercised his lawful authority as president of the Palestinian Authority, as leader of the Palestinian people," Rice said. "We fully support him in his decision to try and end this crisis for the Palestinian people and give them an opportunity ... to return to peace and a better future."
Special correspondent Abu Alouf reported from Gaza City and Times staff writer Boudreaux from Jerusalem. Special correspondent Maher Abukhater in Ramallah, West Bank, contributed to this report.