Several mainland cities, including provincial capitals, are experiencing unprecedented blood shortages, and operations have had to be delayed.

In Kunming in Yunnan province , reportedly the worst-hit city, the blood bank has been below its usual 400,000ml level since July, and on some days as low as 10,000ml, an official said.

'This is the city's severest shortage of donated blood in a decade,' Dr Li Kaihong, director of the centre's blood sourcing division, said. In Qingdao, Shandong province, supplies of both type A and type O blood fell below the warning level. In Nanjing, Jiangsu , hospitals were told to use blood sparingly. Guangzhou, which usually has ample reserves, only has enough to last seven to 10 days, China National Radio reported.

The Beijing Youth Daily cited a hospital chief in Beijing as saying it was common for operations to be delayed for three days to wait for blood.

The Kunming centre, the city's only official blood bank, is responsible for supplying 260 medical facilities. 'Normally, we need 10,000ml of each blood type every day to cover accident and emergency patients and ... scheduled surgery,' Li said. 'Now we have to make accident and emergency patients the priority, and if it is not a particularly bad day and we have some left over ... we will do some scheduled surgery that has been delayed,' she said. 'But we can do only one or two scheduled operations [even] on our lucky days.'

Li said doctors had been asking family members of inpatients to donate blood, which if need be can be exchanged at the Kunming centre for the appropriate type. 'All those whose family members donated blood have received surgery. Those with family members who haven't are still waiting their turn,' she said.

Most clinical blood supplies on the mainland come from voluntary donors, according to the Ministry of Health. Li attributed the sudden drop in supplies to the absence of the biggest group of donors - college students. Many colleges have moved out of Kunming to more remote areas.

'Kunming has long been underpinned by free and voluntary donation of blood. Donations by students account for about a third of the total,' Li said. 'We saw the number of donations start dropping significantly in July, when most students were taking summer break and left town. When the new semester started and they moved to a college town in September, things got worse.'

Some who refuse to donate blood cite health concerns and mistrust of the system. A 29-year-old Beijing housewife who declined to be named said her reluctance to donate stemmed from the belief that she may become infected with a disease.

Government campaigns have stressed safety since people who donated or sold blood in Henan became infected with HIV because of improper procedures, but lingering doubts are apparently strong enough to put off potential donors.