Hamas fighters today basked in triumph after taking complete control in Gaza as the west scrambled for a response to the arrival of Islamist power on Israel's doorstep.
In a stark demonstration of the new facts on the ground, a masked Hamas fighter sat down at the desk of the Palestinian president Mahmoud Abbas, also known as Abu Mazen, and declared an end to the western-backed authority in the Gaza strip.
In an imaginary telephone call to the US, a fighter from the Islamist movement's armed wing, Izz el-Deen al-Qassam, joked: "Hello Condoleezza Rice. You have to deal with me now, there is no Abu Mazen anymore."
In one of its first assertions of authority, Hamas called for the immediate release of the BBC Gaza correspondent, Alan Johnston, who was seized in March.
"He is a guest of the Palestinian people," a masked Hamas official said at a news conference.
Amid scenes of disorder, the deposed Hamas prime minister, Ismail Haniyeh, called for an end to looting of abandoned Fatah properties and proposed reconciliation talks with Mr Abbas.
"I demand that all our people show calm and self-restraint and not take any action against those houses and compounds that contradicts the morals of our people," Mr Haniyeh told reporters before weekly prayers.
In scenes reminiscent of Baghdad after the fall of Saddam Hussein, hundreds of people swarmed through the unoccupied house of Fatah strongman Mohammed Dahlan, after his neighbourhood fell to Hamas, stripping everything, including windows, doors and flowerpots.
"The scenes of Iraq were repeated in every single detail here in Gaza," Hamad Jad told the Associated Press news agency.
Hamas said it would grant an amnesty to a number of senior Fatah officials it had detained.
Among them were Musbah al-Bhaisi, the head of Abbas's presidential guard, Jamal Kayed, chief of the national security forces, Majed abu Shammala, Fatah's senior Gaza political official and the group's spokesman, and old Hamas foe Tawfiq abu Khoussa.
International reaction
As Gaza fell to Hamas control, the European commission threw its full support behind Mr Abbas and called for dialogue to end Palestinian infighting. "We fully support president Abbas," a spokeswoman for the EU executive told a news conference. "We call on president Abbas, the legitimate president of all Palestinians, to make his utmost to resolve the situation through dialogue and to work towards national unity and reconciliation."
She said foreign ministers of the quartet of international peace mediators - the US, the EU, Russia and the UN - would hold a telephone conference during the day to discuss developments in the Palestinian territories.
Britain's foreign secretary, Margaret Beckett, took an uncompromising line towards Hamas.
"The notion that somehow mounting a coup d'etat is something that should be rewarded by the international community seems to me to be completely bizarre," she told the BBC's World At One programme. But she also acknowledged the complexities of the new situation, with the effective creation of two separate Palestinian authorities.
"There is no doubt that what will happen over the coming days is that people will have to consider what can be done, how we can work with the legitimate and legal Palestinian Authority to improve the position on the ground," she said.
"Certainly, finding a way through will not be easy, I accept that, but for the sake of the people of Palestine, we have to try to find it."
The west has boycotted Hamas since it swept to a surprise parliamentary election in January last year, as it considers the Islamist group a terrorist organisation that refuses to recognise Israel or renounce violence.
Israel and the US are expected to ease an embargo on the Palestinian Authority in order to boost Mr Abbas and his secular Fatah group, now that there are two warring Palestinian entities.
The Bush administration is expected to ask Israel to unfreeze tax funds it has been holding back from the Palestinian Authority and to consider loosening its military grip on the West Bank, home to most of the Palestinian population and dominated by Fatah.
Israeli and western officials said the US president, George Bush, and the Israeli prime minister, Ehud Olmert, could agree to send money to the West Bank when they meet in Washington next week.
"If there will be an emergency government without participation of Hamas, then the funds can flow," said a senior Israeli official. "From our point of view, there isn't a Hamas government any more."
While Hamas is in control of Gaza and declaring Islamist rule on Israel's doorstep, the Palestinian quest for an independent state is on the verge of collapse.
Fourteen years after the Oslo accords opened up the prospect of a Palestinian state in the West Bank and Gaza, its putative territory was in danger of breaking into two warring entities. The week of violence between Hamas and Fatah has left almost 100 people, both gunmen and civilians, dead.
Last night Mr Abbas, declared a state of emergency from Ramallah in the West Bank and dissolved the three-month-old "national unity" government as he grasped for a strategy to undermine the "coup d'état".
But Mr Haniyeh of Hamas, said Mr Abbas's decision to dismiss him and his government was "hasty", and he pledged to stay in power.
Mr Haniyeh told a late night Gaza news conference that Mr Abbas and his advisers had not considered "the consequences [of the decision] and its effects on the situation on the ground".
It was unclear how the president could impose his authority in Gaza where the green flag of the Islamic resistance movement was fluttering on many government buildings in the crowded coastal strip.
"We are telling our people that the past era has ended and will not return," Islam Shahawan, a Hamas spokesman, told the movement's radio station. "The era of justice and Islamic rule have arrived."
Qais Abu Leila, a member of the Palestine Liberation Organisation executive committee, said there was determination to take action to stop the "insurrection". "This is a fight to preserve everything that we have built over the last 14 years."
In Ramallah, the seat of the Palestinian Authority, Mr Abbas appointed Salam Fayyad as his new prime minister. Mr Fayyad, who twice served as Palestinian finance minister, worked for the World Bank from 1987 to 1995 and was the International Monetary Fund representative to the Palestinian Authority from 1995 to 2001.
The Bush administration described the Gaza events as "a source of profound concern", accusing Hamas of committing acts of terror. The EU suspended what few aid projects it still maintained there.
The Arab League warned of a "disastrous outcome" to internecine fighting that has been waged on and off for more than six months.
The Hamas victory is widely seen as a boost for Iran and Syria, which have supported the militants, and a painful reversal for the pro-western regimes in Jordan, Egypt and Saudi Arabia, which worry about the Iranian government's meddling in Iraq and Lebanon, as well as Palestine.
Jordan also fears intra-Palestinian fighting could spread from the West Bank and across the river into the kingdom, where at least half the population is of Palestinian origin. "Things have never been so bad," said one senior Arab diplomat.
The Hamas takeover of the Palestinian Authority's security and military intelligence headquarters came after a three-day siege.
Sources close to the Palestinian president said Israel had ignored repeated requests to allow deliveries of ammunition to Palestinian Authority forces, leaving them outgunned by Hamas who have relied on smuggled munitions.
Last night, Hamas said it had executed the top Fatah militant in Gaza, Samih al-Madhoun.
Witnesses said the conquest of the security headquarters was followed by many executions.
The civil war is rooted in a long-standing power struggle between Hamas, which won elections last year, and Fatah, the historic core of the PLO.