Senior cleric Shaikh Abd al-Salam al-Kubaisi said representatives of the Association of Muslim Scholars (AMS), the highest Sunni authority in Iraq, were allowed to enter Falluja on Friday after being barred from doing so one day earlier.
Speaking at a press conference on Friday, spokesperson for the AMS, Dr Abd Al-Salam al-Kubaisi said the situation in Falluja was worsening and accused the US of using cluster bombs.
More than 600 Iraqis have been killed in the last week in Falluja.
"Last night and throughout yesterday, US fighters and helicopters massacred residents of Falluja by dropping banned cluster bombs.
"The people of Falluja were bombed because they were defending their city, land, and honour," al-Kubaisi said.
"The most horrible brutality was the targeting of ambulances which carried pregnant women who were about to give birth. There were tens of bodies which are still under debris and we could not arrive at the places as US snipers prevented people from getting them out," he added.
"Last night and throughout yesterday, US fighters and helicopters massacred residents of Falluja by dropping banned cluster bombs."
Dr Abd Al-Salam al-Kubaisi
Association of Muslim Scholars
"Via you, (addressing the international media) I call on the entire world to see what we are doing and what the US forces have been doing," al-Kubaisi told reporters.
He also accused US forces of detaining and torturing children.
The latest 48-hour extension to the ceasefire expired on Friday and US commanders are due to meet local Iraqi leaders to discuss prospects for a permanent truce.
Blaming each other
But both US forces and Falluja fighters have accused each other of breaking the ceasefire.
Al-Kubaisi warned of a civil disobedience in Baghdad if a peaceful settlement was not found in Falluja.
"The patience of Baghdad residents regarding the Falluja developments has limits and it is possible that a civil disobedience campaign may start," he said.
"What's happening on the ground is very serious," he added, noting that US forces were "digging trenches everywhere in the city".
"Those who want to withdraw do not dig trenches."