By Subir Bhaumik
BBC News, Calcutta
Wildlife authorities in the Indian state of Assam say they are troubled by a sudden rise in poaching of one-horned rhinos at the state's Kaziranga park.
Kaziranga is home to a wide variety of wildlife (Images: Kaziranga centenary website)
They say that they suspect a newly-formed gang of poachers killed six rhinos over the last three months - with two being shot over the last week.
Officials say the problem has been made worse by a lack of wildlife wardens.
Kaziranga is Assam's most famous national park and is estimated to have 66% of the world's one-horned rhinos.
"We suspect that a new gang with better resources is operating in the area," said Kaziranga's wildlife warden Utpal Bora.
The 450 square km (280 square miles) park has nearly 1,900 one horned rhinos - and celebrated its centenary two years ago.
"Kaziranga is a great conservation success. So we are upset whenever poaching intensifies. And now the new group of poachers seem to be very well equipped," Mr Bora said.
Poachers cut high tension lines during power cuts and lay the wires on beaten tracks used by rhinos. The animals tread on to the live wires and die of massive electric shocks.
Police investigations into recent rhino kills also suggest the use of telescopic rifles fired long distance with special armour-piercing ammunition.
The poachers use electric saws to take away the horns without wasting much time. Police says the poachers have some local "collaborators" who know the forest zone well.
"It all indicates the presence of a global poaching racket in Kaziranga. The masterminds are big time players," Mr Bora said.
Rhino horn powder, considered an aphrodisiac, is highly valued in Asia and the horns fetch nearly $40,000 a kilogram. It is also used for Asian medicines and for ceremonial purposes.
There were hardly 20 rhinos left in Kaziranga at the turn of the 20th century when the British declared it a game sanctuary in 1916.
By 1966, their number had gone up to 366. In 1974, the Indian government declared Kaziranga a national park and placed more resources for conservation of the rhinos.
Five to ten rhinos have been killed every year on an average for the past decade.
That's a sharp fall from the early 1990s when up to 50 rhinos were killed a year.
There are not enough wardens at the park
Then, Assam's leading separatist group, United Liberation Front of Assam (Ulfa) started attacking poachers and even executed a few of them after trying them in a "people's court".
The army, while chasing Ulfa guerrillas, also confronted poachers and killed them, suspecting them to be linked to armed rebels.
Now there is little rebel activity around Kaziranga - and the poachers have a free run because there are few armed guards to watch over the sprawling game sanctuary.
MC Malakar, Chief Conservator of Assam Forest (Wildlife Division) says there are 110 posts lying vacant at the Kaziranga, which is now a World Heritage Site.
"Practically no recruitment has taken place since 1994," he said, "while the older generation of expert foresters is retiring, and not able to pass on their knowledge and skills to the new generation."
Officials say that rhino poaching is not the only problem that Kaziranga faces - timber smuggling is also on the rise.
Utpal Bora says the forest department has asked for more armed guards, better weapons and more watch towers to check poaching.
Kaziranga contains one-third of the world's one-horned rhinos
But forest officials say they have not got what they wanted because of Assam's chronic budgetary constraints.
Rhinos are not the only animals in Kaziranga. It has a high concentration of Royal Bengal tigers, Asiatic elephants and Asiatic buffalos.
According to the last animal count in Kaziranga , the Asiatic water buffalo count is more than 1,500 while the elephants number more 1,000.
"It is amazing mix, and one we have to preserve because this makes Kaziranga an irresistible tourist attraction," says Assam's tourism commissioner Himangshu Das.
A cruise down the Brahmaputra river from Assam's capital Guwahati to Kaziranga has been booked out until next year. Most of those going on it are foreigners.