After a comparatively quiet night, large plumes of smoke were seen rising over Gaza City on Wednesday morning. A house near the centre of the city was ablaze after Israelis bombed the area.
Sameh Akram Habeeb, a journalist and blogger, told Al Jazeera by phone from inside Gaza City that periodic gunfire between Palestinian fighters and Israeli forces could be heard.
Israeli helicopters could be heard firing and at least two big explosions were heard from the western and northern parts of the city, he added.
The Israeli military says six soldiers were injured during clashes overnight.
Al Jazeera's Zeina Awad, reporting from the Israeli side of the Gaza border, said the Israeli public was still largely supportive of the military campaign as the general feeling was that it was going very much in Israel's favour.
Israel says 10 Israeli soldiers and three civilians hit by Hamas rockets have been killed so far in the campaign, a casualty rate that the Israeli public seems willing to accept, our correspondent said.
The conflict has left 4,530 Gazans wounded, Palestinian medics say.
Painting a bleak picture of the conflict, Robert Fisk, the Middle East expert and author, said he saw no reason for "any optimism at all in the near future, or even in the medium future".
He said no progress can be made, either in the 19-day-old Gaza war, or in the broader Middle East conflict that has continued on and off for more than 60 years, until the issue of the Palestinians is addressed.
"Why are they dispossessed? Why are settlements - colonies for Jews, and Jews only - being built on Arab land, illegally? And still it continues," he told Al Jazeera.
"Unless we deal with this, there will not be an end to this war. There might be a ceasefire in Gaza, a ceasefire in the West Bank, but there will not be an end to the war. That is the problem."
The United Nations security council had earlier in the week issued a binding resolution calling for an immediate ceasefire in the Gaza Strip - a measure that has so far gone unheeded.
But Fisk said Israel would get away with flouting the UN call so long as the US continues to back it.
"And its quite clear from Hillary Clinton's [incoming US secretary of state] most recent comments that its going to continue under [a President] Barack Obama. I see no change, I see no hope at all in the future." he said.