'Israel has opened the gates of hell'

• Founder of Hamas, Sheikh Ahmed Yassin, killed in Gaza missile strike

• Ariel Sharon gave instructions for attack with security cabinet approval

• EU, UN say attack illegal but US called for parties to restrain themselves

• Hamas accuse US for backing assassination

Key quote: "All the Muslims of the world will be honoured to join in on the retaliation for this crime." - Hamas

Story in full: THE Palestinian terrorist organisation Hamas yesterday warned that Israel had "opened the gates of hell" after a missile strike by a helicopter gunship assassinated its elderly founder, Sheikh Ahmed Yassin, as he left morning prayers at a mosque in his wheelchair.

The Israeli security cabinet approved the killing last week, and when intelligence agents spotted Yassin early yesterday morning as he headed out to pray, president Ariel Sharon, gave instructions for the attack to go ahead.

As dawn broke, helicopters fired three missiles as Yassin, his bodyguards and dozens of others left the neighbourhood mosque in Gaza City. The dead included several bodyguards and Yassin’s son-in-law. Seventeen people were wounded, among them two of Yassin’s sons. Only a charred metal seat and two twisted wheels were left of the cleric’s wheelchair.

The attack brought swift condemnation from the international community. Britain, the European Union and the United Nations all said it was illegal under international law, although the United States restricted its observations to a call for both sides to show restraint.

That seemed increasingly unlikely last night as Palestinian leaders warned of bloody reprisals. There was also concern that it could increase the possibility of attacks on Western targets by Islamic militants.

Within hours of the attack, more than 200,000 Palestinians, some carrying billowing green Hamas flags, poured on to the streets to mourn the death of their blind, wheelchair-bound leader.

As his body was carried to the grave between two rows of 400 militants, armed with anti-tank missiles and machine guns, two Israeli helicopters flew above, and the sky was blackened from the smoke of burning tyres.

Hamas warned that it would have its revenge on Mr Sharon. The attack, it said, had "opened the gates of hell and nothing will stop us from cutting off his head".

Ismail Haniyeh, a close Yassin associate, said: "Words cannot describe the emotion of anger and hate inside our hearts."

And for the first time, Hamas also threatened the United States, saying American backing of Israel made the assassination possible.

"All the Muslims of the world will be honoured to join in on the retaliation for this crime," the group said in a statement.

But Israel was unrepentant. Mr Sharon described Yassin as the "mastermind of Palestinian terror" and a "mass-murderer who is among Israel’s greatest enemies".

Deliberately echoing the language used by Britain and the US when referring to al-Qaeda, Sharon said Israel will press ahead with its war on terror, signalling there would be more targeted attacks and raids. "The war against terror has not ended and will continue day after day, everywhere," he said.

Since Yassin founded Hamas in 1987, the group has killed hundreds of Israelis in scores of attacks. Hamas wants to destroy the Jewish state, replacing it with an Islamic one. Its stronghold is in Gaza, where it has curried loyalty from impoverished Palestinians by offering an array of social services

The foreign ministers of Jordan and Syria changed their schedules to fly to Cairo for urgent talks with their Egyptian counterpart, Ahmed Maher. The matter was also due to be discussed by representatives of the US, Russia, the European Union and the United Nations in the US embassy in Cairo last night.

The Palestinian prime minister, Ahmed Qurie, said the killing had opened the door to chaos.

"It is a clear message to the world that the Israelis are not ready to sit with the Palestinians for peace," he said.

The Palestinian leader Yasser Arafat, Yassin’s biggest political rival, said he feared he would be the next target. An Arafat aide said: "He feels his turn is next and he is sad and worried."

Kofi Annan, the UN secretary-general, condemned the killing: "Such actions are not only contrary to international law, but they do not do anything to help the search for a peaceful solution," he said. "I appeal to all in the region to remain calm and avoid any further escalation in tensions."

Jack Straw, the Foreign Secretary said the assassination was "unacceptable, it is unjustified and it is very unlikely to achieve its objectives".

Jordan’s King Abdullah II said the killing "annoyed and pained" him. It was "a crime" that would lead only to more violence.

Bashar Assad, the Syrian president, condemned it as "the climax of terrorism that Israel is continuously practising".

But the US national security adviser Condoleezza Rice offered no condemnation of the attack: "It is very important that everyone step back and try now to be calm in the region," she said. She said that the US had no advance warning of the attack.

Fearing reprisal attacks, Israel sealed off the West Bank and Gaza and confined many West Bank Palestinians to their communities. The Rafah border crossing between Gaza and Egypt was also closed. Troops were sent to Gaza, and security forces in Israel were placed on high alert.

In addition to Yassin, 12 Palestinians were killed, seven in the air strike, four in clashes with Israeli troops and one while handling explosives.

About 18 billion was wiped from the value of blue-chip shares as the killing of Yassin further increased the pressure on world markets.