"Six rhinos poached in about 100 days, including two of the beasts killed in the past week, is a matter of grave concern. A security alert has been sounded," park warden Utpal Bora said.
The 430 square-kilometer (166 square-miles) park, 220 km east of Assam's main city of Guwahati, is now home to the single largest population of the one-horned rhinoceros.
As per latest figures, some 1,855 of the worlds estimated 2,700 such herbivorous beasts lumber around the wilds of Kaziranga -- their numbers ironically making the giant mammals a favourite target for poaching.
"We are certain that the recent cases of hunting the rhinos for their horns were done at the behest of a very organized international poaching syndicate who has pumped in lot of funds to attract shooters to kill the animals," the warden said.
"We have mobilized all the resources available and have stepped up security in the park. The local villagers have joined us in our fight against poaching," another park ranger said.
Organized poachers kill rhinos for their horns, which many believe contain aphrodisiac qualities, besides being used as medicines for curing fever, stomach ailments and other diseases in parts of South Asia.
Rhino horn is also much fancied by buyers from the Middle East who turn them into handles of ornamental daggers, while elephant ivory tusks are primarily used for making ornaments and decorative items.
Profits in the illegal rhino horn trade are staggering, rhino horn sells for up to 1.5 million rupees per kilogram in the international market.
The fresh incidents of poaching come at a time when park authorities believed the endangered one-horned rhinos were charging back from the brink of extinction.
"There was a time when poachers slaughtered about 50 rhinos annually in the early 1990s. But things have slowed down in recent years due to stepped up vigil and now all off a sudden we see a spurt in poaching again," Bora said.
Five rhinos were poached last year, while seven were killed in 2005.
According to government estimates about 500 of the beasts were killed by poachers during the past two decades.