It is increasingly hard for Iraqi aid workers to help tens of thousands of people caught up in fighting in Baghdad, according to Unicef.
The Sadr City area of the capital has seen the worst clashes between government forces and Shia militia.
The UN children's agency says over 150,000 people there are having difficulty accessing clean water, food and other essential services.
The Iraqi government says almost 1,000 people have died in recent fighting.
Most of those have been civilians, and aid agencies say around 60% of them are women and children.
Medical shortages
For seven weeks now Iraqi forces, backed up by US troops, have been trying to disarm Shia militiamen, but they have faced stiff resistance.
Unicef is warning that tens of thousands of people are at risk because they cannot freely move within their communities, cut off from clean water and food supplies by snipers or by roads laced with improvised explosive devices.
Fighting has severely damaged water and sewage pipes, posing serious health risks.
Hospitals are reporting shortages of medical supplies, while other health facilities open and close depending on the ability of staff to turn up for work, and are often in locations too dangerous for patients to use.
Unicef wants better access to those in need, and is working hard with the government to get water tankers into affected areas and medical supplies to hospitals and clinics.
The agency is also reporting one other worrying development stemming from the current conflict.
It says there are unconfirmed reports that children are being recruited by Shia militiamen into their ranks.