Amman, Jordan ? The U.S. and British military must crack down on the chaotic looting in Iraqi cities, which has even targeted the United Nations’ own offices in Baghdad, U.N. officials said Wednesday.

In Baghdad and Basra, Iraq’s two biggest cities, gangs of civilians were pillaging government offices, empty schools, shops and other buildings and making off with almost anything — from desks and chairs to mattresses and refrigerators.

Television images caught Iraqis driving around Baghdad in stolen U.N. vehicles. Looters had rifled through the headquarters of the U.N. arms inspectors on Baghdad’s outskirts, said David Wimhurst of the U.N. humanitarian office for Iraq. The inspectors, who departed Iraq just before the U.S.-British invasion on March 20, shared the building with the humanitarian mission.

Occupying military forces “have responsibility under international humanitarian law to maintain a secure environment for the civilian population,” said Wimhurst, who is temporarily based in the Jordanian capital.

He said U.N. officials had raised their “very serious concerns” to the U.S. and British military in Kuwait, but did not receive an immediate response about what steps might be taken to restore law and order.

The security breakdown kept some Baghdad hospital workers at home, worsening an already critical situation for war-wounded.

“Reports from Baghdad tell of serious civilian casualties and growing pressure on hospitals and health workers,” said Fadela Chaib of the World Health Organization.

The International Committee of the Red Cross said some medical facilities no longer had water or electricity, their emergency supplies and systems having run out or failed.

The Red Cross was not maintaining a cumulative count, but in recent days it reported hundreds of Iraqi war casualties daily in Baghdad. There was no breakdown of civilian versus military casualties.