Israel has declared a unilateral cease-fire, ending a 22-day offensive on the Gaza Strip that Palestinian health officials say killed more than 1,200 people - many of them civilians.  However, Hamas says the declaration is not enough and is vowing to fight on.

The announcement of a cease-fire came late Saturday from Israeli Prime Minister Ehud Olmert in Tel Aviv. Mr. Olmert said that on Saturday, all the conditions had been created such that Israel's aims, as set earlier, were attained fully, and beyond.

Israel's goals were to destroy Hamas' ability to launch rockets at civilians in southern Israel and to prevent the group from rearming, by sealing off tunnels that Hamas had used to smuggle weapons into Gaza.

The Israeli leader said Hamas militants had been - in his words - badly beaten and Israeli forces have severely damaged their ability to fire rockets at southern Israel.  He said Israeli troops would remain in Gaza for now.

Hamas has demanded a quick and complete pullout of Israeli soldiers from Gaza and a reopening of all of Gaza's border crossings. Officials with the militant group late Saturday said Israel's unilateral declaration was not enough for Hamas to give up its fight. At least one rocket fired from Gaza landed in Southern Israel in the minutes after Mr. Olmert's announcement of a cease-fire.

The decision to end the offensive came at a meeting of Israel's security cabinet Saturday.  The Israeli Prime Minister apologized to the people of Gaza for the heavy civilian casualties inflicted by Israeli forces, and said Israel would help with humanitarian and recovery efforts. "We regret very much the fact that there were so many who, in spite of the genuine efforts made by the Israeli army, suffered from this confrontation.  I want to apologize on behalf of the government of Israel for everyone who was unjustly affected, in Gaza, by this operation," he said.

The apology might not be enough to quiet U.N. calls for a war crimes investigation of Israel, especially after an Israeli tank fired on a U.N. compound, killing two boys who - along with more than a thousand other people - had taken refuge there.U.N. Secretary General Ban Ki-moon earlier Saturday expressed outrage over the incident. "I condemn, in the strongest terms, this outrageous attack which is the third time that this has happened.  The top Israeli leaders have apologized and had given me their assurances, just two days ago while I was visiting Israel, that U.N. premises would be fully respected.  I strongly demand a thorough investigation into these incidents and the punishment of those who are responsible for these appalling acts," he said.

Egypt, which has been trying to broker an agreement between Israel and Hamas, has called a meeting of European leaders on Sunday to discuss the truce and recovery efforts in Gaza.