Ban Ki-moon welcomed the truce - the first peace in the small Palestinian territory since a previous agreement collapsed on August 19 - and warned Israeli officials and militants in Gaza that "after 50 days of profound human suffering and devastating physical destruction, any violations of the ceasefire would be utterly irresponsible," his spokesman said. The ceasefire began at 1600 UTC Tuesday, ending seven weeks of widely criticized bloodshed that killed more than 2,100 Palestinians, most of them civilians, including about 400 children.

"The secretary-general remains hopeful that the extended ceasefire will act as a prelude to a political process as the only way of achieving durable peace," UN spokesman Stephane Dujarric said.

Shortly after the ceasefire came into effect on Tuesday, thousands took to the streets of Gaza to celebrate the apparent end of nearly two months of fighting. Correspondents reported that the loudspeakers of mosques blared out chants normally reserved for Islamic holidays.

'Durable and sustainable'

On Tuesday, Secretary of State John Kerry said that US officials hoped the ceasefire agreement would "prove to be durable and sustainable." He added that the United States would provide humanitarian aid and work with Palestinian Authority President Mahmoud Abbas on the reconstruction of Gaza. Like the UN secretary-general, Kerry called on all parties to abide by the agreement.

"We are all aware that this is an opportunity, not a certainty," Kerry said on Tuesday, citing the challenges in forging a long-term solution acceptable to all parties.

In addition to the 2,100 people killed in Gaza, the past seven weeks saw more than 17,000 residences destroyed, leaving 100,000 homeless, according to UN estimates. Sixty-four Israeli soldiers were killed in combat, and rockets launched from Gaza by militants left four civilians dead. There has been talk of an investigation by the International Criminal Court into atrocities committed by both sides.

Ban urged Israel and the Palestinian political faction Hamas to address the root causes that have led to three wars in six years in Gaza. Ban added that the United Nations stood ready to support efforts to address the "structural factors of conflict" between Israel and Hamas, according to UN spokesman Dujarric.

The secretary-general cited the return of the Palestinian Authority to Gaza, where Hamas has ruled since 2007, the lifting of the blockade imposed by Israel after the faction's takeover, and addressing security concerns as the keys to avoiding a relapse into war. Reiterating that permanent peace could only come through a two-state solution, Ban called on Israeli and Palestinian officials to return to negotiations on a final deal to end the occupation.

mkg/jm (Reuters, AFP, dpa, AP)