International efforts to finalise a ceasefire are being stepped up after a night of renewed Israeli air strikes in Gaza and sporadic Hamas rocket attacks.
US Secretary of State Hillary Clinton is due to visit the West Bank and Cairo following talks with Israeli leaders.
Palestinian sources had suggested a truce would be announced on Tuesday, but Israel said no deal was struck.
Some 136 Palestinians and five Israelis have been killed since the flare-up began eight days ago, officials say.
On Tuesday alone, the conflict claimed the lives of at least 20 Palestinians and two Israelis.
UN Secretary General Ban Ki-moon is also visiting leaders in the region trying to cement a ceasefire.
In the early hours of Wednesday, BBC correspondents in Gaza reported hearing loud explosions that were followed by a widespread power cut.
The BBC's Rushdi Abualouf said eight missiles had destroyed the main complex of a Hamas-run government department in the centre of Gaza City and the shattered building was on fire. Broadcaster Al Jazeera's nearby office was damaged by the blast.
The Israeli military later tweeted it had "surgically targeted a Hamas intelligence operations centre" on the seventh floor of a media building.
Foreign journalists inside Gaza reported a loud explosion that blew in windows at the Deira Hotel.
Hours earlier, French news agency AFP said a building in Gaza City housing its office was hit by an Israeli air strike. No staff members were injured.
Israel's military said it had attacked more than 100 "terror sites" in Gaza overnight "of which approximately 50 were underground rocket launchers".
The Israel Defense Forces (IDF) said it had also attacked the ministry of internal security, which it described as a command and control centre for Hamas.
The health ministry in Gaza said 15 more people had been injured overnight.
The BBC's Jon Donnison in Gaza says the streets were again empty on Wednesday morning, as people tried to protect themselves at home while waiting for something positive to come from talks in Cairo.
Israel says more than 800 rockets have been fired from Gaza into Israel over the past week, 162 in the past day alone.
Many of the rockets have been intercepted by Israel's Iron Dome missile defence system.
Overnight, two rockets were knocked down by Iron Dome and others landed on open ground, Israel Radio said. By morning, air raid sirens sounded in many parts of southern Israel, local media reported.
Egyptian and Palestinian officials had said on Tuesday that a ceasefire would shortly be announced at talks in Cairo.
But Israeli spokesman Mark Regev told the BBC a deal was not yet done.
"I have no doubt that Hamas would be more than happy to have a temporary respite - a time out... so they could rest and re-arm and we would have missiles on Israel next week or next month. We are not interested in that," he said.
US state department spokeswoman Victoria Nuland said Mrs Clinton - who flew into Jerusalem late on Tuesday - had held two hours of talks with Israeli Prime Minister Benjamin Netanyahu and other Israeli officials.
"They discussed efforts to de-escalate the situation and bring about a sustainable outcome that protects Israel's security and improves the lives of civilians in Gaza," Ms Nuland said.
"They also consulted on her impending stops in Ramallah and Cairo, including Egyptian efforts to advance de-escalation."
Speaking just before the talks, Mr Netanyahu said Israel wanted a diplomatic solution but that he was ready to take "whatever action" was necessary.
"If there is a possibility of achieving a long-term solution to this problem by diplomatic means, we prefer that. But if not, then I am sure you will understand that Israel will have to take whatever actions are necessary to defend its people," he said.
The contents of the ceasefire plan brokered by Egypt are not known, but both Israel and Hamas have presented conditions.
Israel's demands include no hostile fire of any kind from Gaza and international efforts to prevent Hamas from re-arming, while Hamas is demanding an end to the blockade on Gaza and targeted killings by Israel.
Israel launched its current offensive a week ago with the killing of Hamas military leader Ahmed Jabari. The Israeli government says his assassination, and the subsequent offensive, aims to end rocket fire from Gaza.
Israel insists it is not trying to topple Hamas - the militant Palestinian group that has governed the Gaza Strip since 2007.
Israel has troops massed along the Gaza border but says it is holding off on a possible ground invasion as talks continue.