GENEVA -- The United Nations top human rights official on Tuesday denounced the killing of civilians and injured people in Fallujah, saying violators of international humanitarian law must be brought to justice.

Louise Arbour, the U.N. high commissioner for human rights, spoke in general terms and did not specifically mention insurgents' attacks against hostages or a U.S. military report that it is investigating the videotaped fatal shooting of a wounded man by a U.S. Marine in a mosque in Fallujah.

"There have been a number of reports during the current confrontation alleging violations of the rules of war designed to protect civilians and combatants," Arbour said in a statement.

"All violations of international humanitarian law and human rights law must be investigated and those responsible for breaches - including the deliberate targeting of civilians, indiscriminate and disproportionate attacks, the killing of injured persons and the use of human shields - must be brought to justice, be they members of the multinational force or insurgents," Arbour said.

She also complained of she said was a lack of independent access to civilians trapped in Fallujah during the U.S.-led assault and an absence of information on the number of civilians casualties.

A relief convoy of ambulances and supplies was unable to enter Fallujah because of fighting in the city Monday, Red Crescent officials said.

Rana Sidani, a spokeswoman for the International Red Cross, said that no international relief organizations have been able to enter the city since the assault began more than a week ago.

"We are sure that there are civilians in Fallujah," Sidani said. "There are injured without access to medical care."

She said the Red Cross, whose mandate is to protect victims of war, knew there were civilians inside the city because it had been in telephone contact with them.

People who reached safety have told the Red Cross they had to leave civilians behind, Sidani said. "They tried to leave but were prevented from doing so," she said.

Sidani said she didn't know whether the civilians left behind were men or whether there were also women and children.

"This is the problem," she said. "There is nobody (to observe) in there."

"Whether they are women and children or men, they are protected under international humanitarian law. Even if they are men and participating in the conflict and are injured. Once they are injured, they are protected," she said.

Marie Heuze, spokeswoman for U.N. offices in Geneva, said the entire "United Nations is following what's happening in Fallujah with deep concern."

The World Health Organization has provided supplies to the Iraqi Health Ministry, including 50,000 blood bags, officials said. UNICEF will provide drinking water to Fallujah residents who fled to the outskirts.

The U.N. refugee agency and the International Organization for Migration have provided tents and other supplies for the displaced.

Christiane Berthiaume, spokeswoman for the United Nations' World Food Program, said "Iraqi institutions have the capacity to provide food through the public distribution system, which is functioning as required and with which we will assist."

Associated Press Writer Jonathan Fowler contributed to this report.

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