OCCUPIED JERUSALEM, 3 December — The Palestinian leadership declared a state of emergency in the Gaza Strip and West Bank yesterday after an unprecedented string of bomb attacks that killed 27 people over the weekend. The emergency suspended all laws, giving police sweeping powers to arrest Palestinian activists.

Security sources said that thousands of police and troops were preparing to take to the streets to confiscate illegal weapons and arrest activists from the Hamas and Islamic Jihad groups. It is the first time a state of emergency has been declared in the Palestinian territories, where self-rule was launched in 1994.

“The Palestinian leadership announces a state of emergency in all the Palestinian territories and has given orders to the Department of General Security to enforce the law and implement emergency measures effective immediately,” the leadership said in a statement.

The leadership, chaired by Palestinian leader Yasser Arafat, groups the Palestinian Authority’s Cabinet and the executive committee of the Palestine Liberation Organization. Under the measures, police will “pursue and detain ... the planners and executors” of the devastating attacks that have prompted dire warnings from the Israelis to the Palestinians to crack down on activists or face a major military response, the leadership said.

“The leadership considers any group that does not adhere to its decisions, especially those that serve the goals of extremist forces in Israel, as illegal, particularly those that claim responsibility for the attacks and bombings against civilians in Israel,” said the statement.

“Until the state of emergency is over, we will put the police and the army in the streets, establish checkpoints, and confiscate any illegal weapons in the streets,” a senior security source said. “We’ll arrest all those who hold illegal weapons or are responsible for the planning of any violent acts, committed or yet to be committed,” he said. “There will be no assemblies, no demonstrations, no nothing.”

Asked what will happen to members of groups who refuse to hand over their weapons or resist arrest, he said, “They will be brought in by force.”

However, he said the state of emergency was “a temporary measure, it’s for a specific period for things to be done.” “Nobody knows how long, but I expect three or four days, no more,” the security source said.

The tough words amounted to a declaration of war on the largest Islamic resistance group, Hamas, which claimed responsibility for Saturday night’s bombing in Jerusalem and yesterday’s bomb blast on a Haifa bus.

Twenty-seven people, including three bombers, died in the two explosions, according to the latest toll issued by hospitals. The bombings were among the deadliest attacks in Israel in years and marked one of the bloodiest phases of a 14-month-old Palestinian uprising against Israeli occupation. They threatened to wreck a new US peace mission led by envoy Anthony Zinni.

Leading fierce international criticism of the attacks, US President George W. Bush condemned the bombings before talks with Israeli Prime Minister Ariel Sharon in Washington. “This is a moment where the advocates for peace in the Middle East must rise up and fight terror. Chairman Arafat must do everything in his power to find those who murdered innocent Israelis and bring them to justice,” he said.

Hamas said the attacks were to avenge Israel’s Nov. 23 murder of Mahmoud Abu Hanoud, a Hamas military leader. The Palestinian security source said dozens of activists had been arrested since Saturday night across the West Bank and Gaza Strip.

Israeli Foreign Minister Shimon Peres said Arafat would be tested “by deeds alone” and that the Palestinian leader’s previous arrests had proved a “farce”. “This may be the most serious crisis in Israel-Palestinian relations,” a Foreign Ministry statement quoted Peres as saying.

The Israeli Army responded to the bombings by tightening its blockade of the West Bank and encircling Palestinian cities it had not already surrounded.

Israel said it held Arafat directly responsible for the attacks. The Palestinian Authority condemned the bombings, which it said were intended to foil peace efforts. The rapidity of the attacks reminded Israelis of a series of suicide bombings in quick succession in early 1996 which killed dozens of Israelis in response to Israel’s killing of a top Hamas activist with a booby-trapped cell phone.

Arab League Secretary-General Amr Moussa said the bombings were the latest in a “regrettable” exchange of attacks and retaliations between the two sides. Moussa added that neither side should target civilians, the state-run MENA news service reported.

“It is said that what happened today in Haifa was a response to the death of a Palestinian political figure, whom the Israelis killed in accordance with an official Israeli list,” Moussa was quoted as saying. “It is clear that as long as the Israeli government continues with its list the responses will continue... It is unfortunate because in both cases, action and reaction, civilians are exposed,” he said.

“It is a matter of principle that civilians should remain outside the conflict and this applies to Palestinians and Israelis both,” Moussa said.

Condemning the bombings in Israel as acts of terrorism, UN Secretary-General Kofi Annan told Palestinian leaders to take immediate and decisive action to punish those responsible for the carnage. He said he was “shocked and horrified” by the attacks, emphasizing that no cause could justify the deliberate murder of innocent civilians and said the assaults undermined those on all sides working for peace and justice, according to a statement issued by a UN spokesman.