Casualties have been pouring into over-stretched hospitals in the Gaza Strip as Israel presses on with its offensive against Palestinian militant groups.
Palestinian medical officials said earlier that 90 people, including many civilians and 26 children, had died since Israel's ground assault began.
Israel says it is targeting militants continuing to fire rockets into Israel.
Intense diplomatic efforts are under way to resolve the crisis, but Israel rejected calls for an immediate truce.
French President Nicolas Sarkozy, who is on a mission to the region, appealed for a halt to the violence to allow humanitarian aid through.
There were reports of fierce fighting in northern Gaza on Monday as news began to emerge of the scale of the problems facing medical staff in the territory.
Dr Khamis al-Essi, an emergency doctor at Gaza's biggest hospital, al-Shifa, said they were struggling to cope with the huge numbers of casualties.
He said they had received "all sorts of casualties, from shattered bodies, beheaded individuals and patients with superficial cuts and lacerations".
"Most of the injuries affected civilians, especially women and children," he told the BBC.
The BBC's Rushdi Abou Alouf, reporting from inside the hospital, said he had seen as many as 900 people being treated.
The doctors say they are running out of medicine, and there is a severe shortage of all essential medical and blood supplies across Gaza, he says.
Among the dead was a family of seven killed by an Israeli air strike in a refugee camp east of Gaza City, health officials said.
Dr Essi said many families were in need of ambulances, but medical workers were struggling to reach casualties because they were being shot at.
Israel insists it is not targeting civilians, and accuses Hamas of using civilians as human shields by operating in densely-populated areas.
Fighting was reported around Beit Hanoun and Jabaliya, and Gaza city itself - a little further south - was said to have been encircled.
Another BBC journalist in Gaza, Hamada Abu Qammar, said residents on the edges of the city were heading into the city centre seeking safe places away from the fighting.
The Israeli army said it hit 40 targets in the Gaza Strip on Monday, including several tunnels and the homes of a number of Hamas officials.
There were also reports that troops had pounded mosques they believe are being used as weapons' stores and seized a main highway, effectively slicing the territory in two.
But information about what is happening is limited as Israel has barred foreign reporters from entering Gaza.
Palestinian medical sources say the number of people killed in Gaza now stands at more than 500, with some 2,500 wounded. These figures cannot be independently verified.
Five Israelis have been killed since the start of Israel's military operation 10 days ago.
Israeli Defence Minister Ehud Barak said Hamas had suffered a "hard blow", but insisted the offensive in Gaza would continue.
"We still haven't reached our objectives," Mr Barak told Israeli MPs.
A spokesman for Hamas' military wing, identified as Abu Obeida, said "thousands" of fighters were ready to battle Israeli troops inside Gaza.
And he said rocket attacks on Israel would continue.
The Israeli army said Palestinian militants fired 20 missiles into southern Israel on Monday.
For the people of Gaza, living conditions are deteriorating sharply. Supplies of fuel, food, water, and wheat are said to be running desperately low.
A spokesman for Unrwa, the UN aid agency for the Palestinians, said food was urgently needed and people were facing "serious hunger", with supplies for just 48 hours.
"One million people are without electricity. Crucially the hospitals in Gaza are running on emergency generators. This in my book amounts to a humanitarian crisis," Christopher Gunness told the BBC.
Israel said it had allowed a convoy of 80 lorries carrying food and medicines through Gaza's southern frontier.
Away from the frontline, diplomatic efforts to halt the fighting in the Gaza Strip have been moving into high gear.
French President Nicolas Sarkozy held talks with Palestinian leaders in the West Bank town of Ramallah at the start of series of meetings across the Middle East.
In remarks broadcast on French radio, he "condemned" the Israeli ground offensive but said Hamas had also "acted in an irresponsible and unforgivable manner" by ending a six-month ceasefire with Israel and resuming firing rockets.
US President George W Bush also blamed the current situation on Hamas militants.
"Instead of caring about the people of Gaza, Hamas decided to use Gaza to launch rockets to kill innocent Israelis," he said.
An EU delegation met Egyptian President Hosni Mubarak in the Red Sea resort of Sharm el-Sheikh on Monday before heading to Israel for talks with Israeli Foreign Minister Tzipi Livni.
"The EU insists on a cease-fire at the earliest possible moment," said Karel Schwarzenberg, the foreign minister of the Czech Republic, which took over the EU's presidency last week.
But Ms Livni appeared to rebuff the call, saying: "When Israel is being targeted, Israel is going to retaliate."
"Israel is going to give an answer to it because this is an ongoing, long battle, war, against terror."
التسميات: english, news