The Swiss-based International Committee of the Red Cross has resumed aid operations in the Iraqi capital, Baghdad, after a one-day break.
But the organisation says the situation in Baghdad is chaotic and dangerous with widespread looting, including in the city's hospitals.
The ICRC's Florian Westphal told swissinfo that an ICRC delegation had gone out on Thursday into Baghdad to assess the situation but had found widespread looting and a heavy presence of armed people in the streets.
"Some hospitals have been attacked by armed looters and one of them - the Al-Kindi hospital - has been completely ransacked: people have taken away even essential items such as beds and electrical fittings," said Westphal.
"That raises the concern that much of the population will find it impossible to have access medical care from these hospitals, mainly because they'll be too afraid to even get there," he added.
Westphal said the volatile situation meant that the ICRC delegation was unable reach hospitals and distribute additional drinking water to parts of Baghdad not connected to the water network, as it had planned on Thursday.
Call for help
The ICRC said measures should be taken to counter the crisis.
"We would like coalition forces to do everything in their power to primarily protect important public infrastructure, such as the hospitals [and] the water supply system," said Westphal.
But he added that the aid organisation would be continuing its work in Baghdad, despite the volatile situation and underlined that it would make every effort to ensure the security of its staff.
"We've already had a deeply tragic and unfortunate loss of one of our colleagues and we'll do all we can to stop a similar thing from happening," Westphal told swissinfo.
The return to operations follows a one-day halt by the organisation after one of its workers, a Canadian, Vatche Arslanian, was killed in crossfire between United States and Iraqi troops on Tuesday.
Medicins sans Frontieres, an aid agency also known as Doctors without Borders, has also reported two of its staff missing since April 2.
The Iraqi regime lost control of the country's capital, Baghdad, on Wednesday, to United States forces, which are in the heart of the city.
The result has been a breakdown of law and order in the capital.
The Swiss Agency for Development and Cooperation (SDC) said on Thursday that it wouldn't be returning to Iraq for the foreseeable future due to security fears.
"We're really worried - as are the UN and other humanitarian organisations - about security, " said Joachim Ahrens of the SDC.
"The death of the ICRC worker has not only affected us but it also shows how insecure the areas still are," he added.
He said that a SDC coordinator would continue supporting the ICRC in neighbouring Amman and that three infrastructure experts from the UNHCR, the United Nations refugee agency, were on call in Iran.
The SDC has already set aside SFr7.5 million for aid to Iraq this year of which SFr1 million has been given to the ICRC.
swissinfo, Isobel Johnson
The ICRC has resumed aid operations in the Iraqi capital, Baghdad, after a one-day break.
But the organisation says the situation in Baghdad is chaotic and dangerous.
It has reported widespread looting, including in the city's hospitals.
The ICRC has called on coalition forces to protect infrastructure.