Dozens of wild peacocks have died suddenly in Pakistan, prompting experts to fear an outbreak of the highly contagious Newcastle disease.

Officials on Monday confirmed the deaths of at least 60 peacocks in Thar desert, part of southern Sindh province, over the last week. Local media reports say more than 100 of the exotic birds have died.

The wildlife ministry said tests were being done to diagnose the cause of death, but said the wild peacocks had been weakened by starvation, deforestation and a lack of safe drinking water blamed on delays to the annual monsoon rains.

"Wild peacocks have become susceptible to bacterial and fungal attack, which further suppressed the immunity of the birds that paved the room for viral attack," it said.

Experts are alarmed by the number of deaths, suspecting they may have been afflicted with Newcastle disease, known locally as ranikhet.

"We are vaccinating wild peacocks protectively for suspected viral disease, as in 2003 when a few peacocks died from the same symptoms that later proved to be ranikhet," said Lajpat Sharma, an official in the provincial wildlife ministry.

Tahir Qureshi of the International Union for Conservation of Nature (IUCN) also told AFP that he suspected ranikhet was to blame.

Newcastle disease is a worldwide problem among birds and sporadic outbreaks can occur frequently. Affected birds suffer from loss of appetite, coughing, sneezing, diarrhoea, and in severe outbreaks a high proportion die.

The wildlife ministry said it was supplying fresh water to peacocks in affected areas.

Sharma said there are at least 30,000 wild peacocks in the Thar desert, but Qureshi said the numbers were declining, because of poaching and lack of effective conservation.