The Red Cross says it has serious concerns about the plight of civilians in the Iraqi city of Falluja.
It has called for an independent assessment of conditions in Falluja, where there is still no electricity or tap water.
Iraqi and US authorities, back in charge of much of the city, have played down warnings of a humanitarian crisis.
Meanwhile bomb blasts killed at least four people in Baghdad and Kirkuk, as violence continued across the country.
An Iraqi family flees the destroyed city of Fallujah. (AFP/Patrick
- In western Baghdad, a car bomb explodes outside a police station, killing two people and injuring at least four, police say
- Two Iraqis are killed by an explosion in the rush hour near a recruitment centre in the northern city of Kirkuk
- Rebels fire mortars at government offices
in Mosul, where US troops are trying to put down an uprising by insurgents
Fight to the death
Conditions in Falluja are said to be desperate, after months in which militants held the city, and the US first bombarded what it called rebel positions, then invaded.
An ICRC spokesman told BBC News that Falluja's main hospital, on the outskirts of the city, had been freshly stocked with medical equipment, but that wounded people could not get there.
"The first concern we have is over the safety of the people in Falluja," Ahmed Rawi said.
"We simply cannot enter the city under such ferocious fighting."
He said the ICRC was negotiating with US forces to open a "humanitarian corridor" into the city.
The BBC's Jennifer Glasse, with US marines in Falluja, says tough battles are still being fought in the city's southern neighbourhoods.
She says marines are calling in aerial bombing raids to hit houses where insurgents are holed up, refusing to surrender.
The marines' commander says at least 55 insurgents were killed on Wednesday.
In nearby Ramadi, US forces were said to have fought a three-hour gun battle overnight, in which at least seven people were reported killed.
Several people were killed in a day of violence across Iraq on Wednesday, including at least 14 Iraqis who died in a suicide bombing in the town of Baiji, north of Baghdad.
The supreme leader of neighbouring Iran, Ayatollah Ali
Khamenei, on Thursday condemned "the massacre of civilians, women and children... the execution of wounded, the destruction of homes [and] mosques" by "infidels" in Falluja.
Meanwhile, a mutilated woman's body found in Falluja on Sunday has been flown out of Iraq for DNA tests to see if it is that of kidnapped aid worker Margaret Hassan.