"Only then can we say conclusively whether the number of tigers has gone up or down," he said on Friday. "The problem is there in some reserves, but in certain reserves sightings have really gone up."

Indian media and wildlife activists have reported a dramatic drop in the number of tigers and an increase in poaching.

On Thursday, Singh chaired a meeting of the national wildlife board -- it's first in 17 months -- and ordered a new taskforce of forest officials, wildlife experts and community leaders to report on the status of Project Tiger and the tiger population,

He also banned giving tigers to foreign dignitaries and established a powerful wildlife crime prevention bureau.

Officials say tigers may have been wiped out entirely in the Sariska sanctuary in the desert state of Rajasthan -- where the Project Tiger conservation programme began in 1973 and where there were as many as 16-18 big cats a year ago.

WAKE-UP CALL

Activists fear the story may be the same in sanctuaries across India, which has almost half the world's surviving tigers.

"It's probably the biggest conservation scandal in modern times," Belinda Wright, executive director of the Wildlife Protection Society of India, said.

"There are some parks with none or so few tigers it's not a viable population. Sariska has been an incredible wakeup call."

Detectives from the Central Bureau of Investigation are due in Sariska on Friday as part of the police probe.

Trade in dead tigers is illegal, but a single one can fetch up to $50,000 on the international market. Organs and body parts are popular in Chinese medicine. Bones are worth about $400 a kilogram, a penis almost $850, a tooth $120 and a claw just $10.

A century ago, there were an estimated 40,000 tigers in India. Now, some wildlife experts say there are barely 2,000 and the official government census about 3,700.

Exact figures are almost impossible because of the shy nature of the big cats. The government keeps no detailed records on poaching, most of which goes unreported anyway.

In Sariska, about 900 vehicles enter the reserve on some days, about 25 times the recommended 35-40 vehicles a day, driving any remaining animals deeper into the forest.

For decades, hunting tigers was a popular sport with British colonial rulers and Indian maharajas. In some areas, tigers were once so common they posed a serious threat to villagers and explorers and people rarely ventured out in the evening unarmed.