Concerns about Ukraine’s ability to provide basic medical care and treat injured soldiers and civilians are growing as the Russian invasion, now in its second week, continues.

Military violence has killed at least 227 civilians and injured more than 500 since the invasion began on Feb. 24, according to the United Nations, which said the numbers are likely an undercount. Russian forces have bombed hospitals, and medical supplies, including oxygen, are running out in besieged cities. The World Health Organization has called for a “humanitarian corridor” to enable aid to reach those in need, but none has yet materialized.

Ukraine’s largest covid wave peaked about a week before the invasion, and health officials have been trying to contain a small polio outbreak. A million refugees have fled the fighting, which could stress neighboring health systems and interrupt routine care.