KABUL, Afghanistan — The United Nations urged all sides of the Afghan conflict to protect aid workers delivering critical assistance to a population caught in relentless violence.

Afghanistan remains among the three most dangerous countries for aid workers, and a recent escalation in violence has often blocked important relief from reaching civilians.

The appeal on Saturday came as the Afghan government and aid agencies began delivering assistance to Ghazni, a city 90 miles south of the capital Kabul which was under a Taliban siege for several days. Hospitals were overwhelmed with casualties and the water supply, electricity, and telecoms were shut down.

“My plea to the Taliban, to everybody engaged in violence in this country, is please respect the work of aid agencies,” Toby Lanzer, the United Nations’ humanitarian coordinator in Afghanistan, said on a visit to a Kabul hospital packed with the wounded from Ghazni and from a suicide bombing targeting an education center in the capital last week.