A 32-year-old herdsman died in Ziketan, a Tibetan area of Qinghai province, according to the province's health authority. It did not specify when he died. The other 11 victims are relatives of the deceased and are in stable condition in hospital, a statement said.

The other 10,000 inhabitants of Ziketan, which covers an area of over 1,000 sq miles on the Tibetan plateau, have been quarantined. A team of medical experts have been dispatched to monitor the disease.

Pneumonic plague is spread through the air and can be passed from person to person through coughing, according to the World Health Organisation (WHO). It is triggered by the same bacteria as bubonic plague, which killed an estimated 25 million people in Europe during the Middle Ages.

Bubonic plague can now be treated with antibiotics, but pneumonic plague remains highly lethal and infectious. The WHO said humans can die within 24 hours of infection.

The Chinese health ministry announced last September that a married couple in western Tibet had died from pneumonic plague.