Israeli air attacks on the Gaza Strip has resumed after a three-hour truce to allow in humanitarian aid, with border tunnels apparently the main target, BBC reported.
Israeli planes leafleted southern Gaza by day, warning of imminent attacks, and the sounds of war could be heard from the border by nightfall.
Nearly 700 Palestinian and 11 Israeli lives are said to have been lost since the offensive began 12 days ago.
Peace efforts move to Cairo shortly, with an Israeli envoy due in the city.
But Israel is prepared to go even deeper into the Gaza Strip in the coming hours, BBC Middle East editor Jeremy Bowen reports from the Israeli border near Rafah.
Our editor could hear the clatter of Israeli helicopters and the report of at least one explosion from inside southern Gaza late on Wednesday night.
"Because Hamas uses your houses to hide and smuggle military weapons, the IDF [Israel Defence Forces] will attack the area," read leaflets released earlier by the thousand over the Rafah area by Israeli planes.
Unconfirmed reports speak of a tank advance with helicopter support towards Khan Younis, also in the south, shortly after midnight.
Israeli security sources have confirmed that senior Israeli defence official Amos Gilad will travel to Cairo on Thursday to discuss ceasefire options.
A Hamas delegation is expected in Cairo at some stage for parallel "technical" talks, Egyptian diplomats said.
Palestinian Authority leader Mahmoud Abbas is expected in the Egyptian capital on Friday.
Israel said on Wednesday it accepted the principles of a Franco-Egyptian truce proposal, which was backed by Washington, but wanted to see the details.
The UN Security Council seemed deadlocked over the crisis.
Arab countries want the Council to vote on a resolution calling for a ceasefire while Britain, France and the US are pushing for a weaker statement welcoming the Franco-Egyptian initiative.
The US could well veto any vote as it is a permanent member of the Security Council, the BBC's Laura Trevelyan reports.
Palestinian health officials say at least 683 Palestinians have been killed and more than 3,085 injured.
Aid agencies report that Gazans rushed into the streets to buy essential supplies and visit relatives in hospital during Wednesday's pause in fighting.
UN aid workers welcomed Israel's promise of brief daily ceasefires but said only a total end to fighting would allow them to distribute aid to those who need it.
More than 20 rockets were fired into Israel from Gaza during the day.
Israel has lost seven soldiers on the ground to date while rockets have killed four people.
Casualty claims in Gaza cannot be independently verified.
While the BBC has had Palestinian producers reporting from Gaza, Israel only allowed Western TV crews to enter on Wednesday, embedded with its army.