Gaza City /Tel Aviv - Top Israeli diplomats were heading for Washington and once again to Cairo to work out the details of a truce in Gaza, as fighting in the strip continued Friday and the Palestinian death toll topped 1,100.

As Foreign Minister Tzipi Livni left Thursday night for the US to sign an agreement on joint intelligence cooperation against weapons smuggling to Gaza, another senior official, Amos Gilad, was returning to Egypt where he had heard Hamas' position on an Egyptian ceasefire initiative on Thursday.

UN Secretary General Ban Ki-moon, who spent the night in Jerusalem, was also due to travel to the nearby West Bank city of Ramallah for talks with Palestinian caretaker Prime Minister Salam Fayyad and Palestinian President Mahmoud Abbas.

Gilad on returning Thursday night headed straight to Jerusalem to brief caretaker Prime Minister Ehud Olmert, Defence Minister Ehud Barak and Livni on what he had heard in Cairo. He was returning Friday with instructions from the trio.

Only after his return from Cairo was Israel's final response on the Egyptian initiative expected.

Hamas announced earlier this week that it had accepted the initiative in principal with certain reservations.

The Israeli Ha'aretz daily said it had obtained a copy of the Egyptian initiative and said it detailed three points:

First, Israel and Hamas will agree to an immediate, time-limited cease-fire, during which humanitarian aid is to enter Gaza, and Egypt will lead indirect negotiations on a longer-term truce;

Second, the long-term truce must include guarantees on border security - an Israeli demand - and an end to the economic blockade of Gaza - a Hamas demand;

Third, Hamas and its bitter rival, Abbas' Fatah party, should resume reconciliation talks that would eventually end the split between the Hamas-run Gaza and the Abbas-run West Bank.

Unconfirmed reports late Thursday suggesting a short-term halt to hostilities in Gaza could start within 72 hours. However, some significant differences remain.

The Dubai-based al-Arabiya news channel quoted diplomatic sources as saying that Hamas accepted "a one-year-long renewable ceasefire on the condition that Israeli troops withdraw from the Gaza Strip within five to seven days."

The stepped-up diplomacy came amid the worst day of fighting in Gaza Thursday in Israel's now 21-day offensive, in which Israel shelled a UN compound, killed one of Hamas' top three leaders in Gaza, and made the deepest advance into Gaza City yet, sparking intense battles with local militants not far from the heart of the city.

One wing of a hospital was also on fire, and two high rises housing international media outlets were hit.

Hamas vowed to avenge the death of its de-facto Interior Minister Said Saim, who also headed its security forces, and declared Friday another "day of rage" calling for protests in the West Bank.

Three shells hit the UN compound in the centre of Gaza City, setting ablaze a warehouse and destroying large amounts of humanitarian aid meant for Palestinian refugees.

The strike came just as the UN's Ban, who expressed "strong protest and outrage" was visiting Israel.

The fighting continued also Friday, with the Israel Air Force attacking another 40 targets overnight and the ground troops continuing to take on militants in Gaza City neighbourhoods, but residents said the morning was relatively quiet compared to Thursday's fighting.

As Israel completed three weeks of its deadly and destructive offensive aimed at curbing more than seven years of rocket and mortar attacks at its southern towns and militants from Gaza, the Palestinian toll reached 1,105 killed and more than 5,130 injured Friday morning.

Ban on Thursday decried the surging toll, saying in a news conference in Tel Aviv that it had reached an "unbearable point" and urging an immediate truce.

Thirteen Israelis, including three civilians, have also been killed since Israel launched the offensive December 27.

Over the past nearly three weeks, Israeli planes and helicopter gunships have attacked well over 2,000 targets, a military spokesman said.

He said Israel had managed to destroy 60 or 70 per cent of the vast network of smuggling tunnels running under Gaza's border with Egypt.

Hamas and other militant factions fired more than 700 rockets and mortar shells into Israel. They fired 25 such rockets and mortars on Thursday.

Israel said it would observe another humanitarian lull Friday and pause its attacks between 10 am and 2 pm (0800 to 1200 GMT).

Some 135 trucks with food and medical supplies were scheduled to enter through its border crossings with Gaza of Kerem Shalom and Karni, while industrial diesel was also due to enter through the Nahal Oz fuel crossing, the military said.