The World Health Organization warns the health system in eastern Ukraine has all but collapsed, putting the lives of thousands of people trapped in Mariupol and other besieged areas at risk.

U.N. health officials say it is critical they be granted immediate access to Mariupol and other areas hardest hit by fighting in eastern Ukraine. They say they have received reports that nearly all health facilities and hospitals in areas like the Luhansk region either are damaged or destroyed.

The WHO is appealing for access to affected areas to assess health needs and to provide critical medical supplies to the sick and injured. Speaking from Lviv in western Ukraine, WHO spokesman Bhanu Bhatnagar said the WHO so far has not been able to enter Mariupol and does not know the health status of the besieged population.

Mariupol has been subjected to relentless bombing and shelling by Russian forces for the past two months. The city has been razed to the ground. Tens of thousands of people reportedly are living in underground bunkers, with limited food, water, and medical supplies.

Bhatnagar said the WHO is moving supplies it thinks are needed in Mariupol closer to the city. But he added it is essential that a safe passage is created quickly.

“We need a cessation of fighting for at least two days in order to move vital supplies in, but also assess the health needs,” he said. “We anticipate the worst. A health system that has collapsed completely and that brings with it all kinds of knock-on effects. Of course, there are people with conflict-related injuries that need help.”

Bhatnagar noted there also are people with chronic conditions and other health care needs that do not have access to vital medicine. He said the findings of a new WHO survey of 1,000 households across Ukraine show the devastating impact this war is having on access to health care.