MOSUL, Iraq, July 27 (UPI) -- Health workers in Iraq say insurgents are holding up hospitals and blood banks at gunpoint to steal blood for their wounded comrades.

The raids by members of al-Qaida in Mesopotamia have been occurring for some time in provinces with large Sunni Arab populations, The New York Times reported Tuesday.

One hospital near the Syrian border had to be closed for several days after doctors and staff received death threats for refusing to cooperate with al-Qaida's demands for blood and other supplies.

Dr. Yaseen Ahmed Abbas, director of the Red Crescent Society in Iraq, said typing and transfusing blood is not an easy procedure.

"Even if you had the same blood type, you'd have to make a perfect match," Dr. Abbas said.

Some doctors working in Sunni areas believe al-Qaida has its own specialists who can perform blood transfusions so insurgents won't risk arrest by seeking treatment at hospitals, The Times said.