Hamas has threatened to retaliate in the occupied West Bank against President Mahmoud Abbas's forces if they did not stop Fatah "terrorism" there against members of the Islamist group.
Hamas official Sami Abu Zuhri said 150 Hamas supporters have been "abducted" in the occupied West Bank following Hamas's bloody takeover of the Gaza Strip.
"What is happening in the West Bank is a real coup and real terrorism," Abu Zuhri said. "We will not stand handcuffed against these crimes in the West Bank. We will take all steps to secure an end to these crimes."
Fatah gunmen stormed the Hamas-controlled parliament in the West Bank today as Mr Abbas prepared to swear in a new government.
Mr Abbas ordered the Hamas-led government to disband on Thursday and will swear in a new administration by tomorrow. However, Hamas said the order amounted to a coup and that Prime Minister Ismail Haniyeh, a Hamas leader, remained in power.
The control of Palestinian territories is now split with Hamas in full control of Gaza, setting up a new security command, while Fatah is in control of the West Bank, taking over remaining Hamas controlled buildings.
An American envoy told Mr Abbas during a meeting today in the West Bank city of Ramallah that the United States would lift a ban on direct aid to the new government. "I think ... there won't be any obstacles, economically and politically, in terms of re-engaging with this (Abbas-appointed) government. Yes, they will have full support," US Consul-General Jacob Walles said afterwards..
A Palestinian militant from the al-Aqsa Martyrs Brigades, an armed wing of Fatah, raises a flag outside the parliament building in Ramallah
About 50 Fatah gunmen and 200 other demonstrators stormed a Palestinian parliament building in Ramallah to protest against Hamas's bloody takeover of Gaza, but no injuries were reported.
The militants grabbed the deputy speaker, who is aligned with Hamas, and dragged him from the building, witnesses said. He was not hurt.
Many Fatah supporters who live in Gaza fear reprisals from Hamas militants after Mr Abbas sacked the Hamas-led government on Thursday. An aide to Mr Abbas said as many as 3,000 Fatah supporters left through the Erez Crossing between Gaza and Israel, but Israeli officials at the crossing disputed that figure.
Other Palestinian officials said hundreds of Fatah supporters were allowed by Israel to exit Gaza through Erez and then travel to the occupied West Bank.
In the West Bank city of Hebron, al Aqsa Martyrs Brigades militants, an offshoot of Fatah, stormed Education Ministry offices, firing in the air and demanding that Hamas supporters stop working there. In Nablus the city council building was also taken over by Fatah.
Arab governments said they would support Mr Abbas and called for a return to the situation before the Islamist movement's bloody takeover of the coastal strip.
Ismail Haniyeh, who became prime minister after Hamas won parliamentary elections in January 2006, has refused to accept his dismissal. In an interview with a French newspaper, he ruled out setting up a Palestinian state in the Gaza Strip separate from the West Bank.
"Separation is not on the agenda and never will be," Mr Haniyeh said. Mr Abbas has tapped Salam Fayyad, a Western-backed independent lawmaker, to serve as prime minister of the emergency government in what Hamas said amounted to a coup.
The United States, Israel and European states plan to open the financial taps to the new government after a 15-month embargo of the Hamas-led administration pushed the Palestinian Authority to the brink of financial collapse.
Palestinian lawmaker Hanan Ashrawi said Mr Fayyad's cabinet faced daunting challenges, chief among them "to ensure the rule of law and to prevent the spread of lawlessness from Gaza to the West Bank."
The security challenge was highlighted in orders issued by Palestinian Police Chief Kamal el-Sheikh, who is based in the West Bank, to his men in Hamas-controlled Gaza. He ordered the police, who have long been dominated by Fatah, neither to report to work nor to follow Hamas's orders.
Hamas's armed wing said it discovered seven bodies today, including Hamas militants and civilians, inside an underground facility that had been controlled by Fatah forces.
Mr Abbas sacked the three-month-old unity government he formed with Hamas on Thursday after the group routed his forces in the Gaza Strip and began imposing a new order in the enclave after days of bloody civil war.
Under Palestinian law, Mr Abbas can declare a state of emergency for up to 30 days. The state of emergency could be extended for another 30 days, but only after winning the approval of two thirds of the parliament.
Hamas has a majority in the parliament - although Israel's arrests of nearly half of Hamas's deputies put that majority in doubt and also make it hard to reach a quorum. That could enable Mr Abbas to keep the state of emergency in place longer.
Some Fatah and US diplomats have argued that Mr Abbas could rule by decree for six months to a year ahead of new elections.