China has issued a health alert in its south-western region of Tibet after five people were diagnosed with the plague, an often fatal infectious disease.

One of the five has already died from a severe lung infection attributed to the pneumonic plague, while one other patient was in a critical condition, the Tibet health department said in a statement on its website.

The outbreak was first detected on Thursday last week in Latok village in Tibet's Nyingchi Prefecture, the department said.

The four patients, all of whom had contact with the deceased, have been quarantined, it said.

Disease control experts have been dispatched to the area in an effort to control the further spread of the disease, it said.

The department also issued a warning to anyone who has visited the region near the outbreak to seek immediate medical attention should they develop fever, cough or other flu-like symptoms common to the plague.

Pneumonic plague is spread by rodents like marmots, which are numerous in Tibet.

An outbreak of the disease last year killed three people in Ziketan, a town in a Tibetan area in neighbouring Qinghai province.

The World Health Organisation says pneumonic plague is the most virulent but least common form of plague. The mortality rate can be high, but prompt antibiotic treatment is effective.

-AFP