A rare one-horned rhino has been killed as poaching attempts increase in one of India's best-known national parks during the coronavirus lockdown, officials said Sunday.

The lack of vehicles on the highway near Kaziranga National Park in Assam state -- home to the world's biggest population of one-horned rhinos -- amid the lockdown has seen animals move towards the boundaries, making them vulnerable to poachers.

"It is suspected that the rhino was killed at least two to three days ago," the park's director P. Sivakumar told AFP, adding that the rhino's horn was also missing.

Hunters can earn as much as $150,000 for one rhino horn or around $60,000 per kilo on a black market according to media reports, serving foreign demand for its use in traditional Chinese medicine. "We have also recovered eight rounds of empty cartridge of AK 47" automatic rifle, Sivakumar said.

The rhino carcass was found near a water body inside the park, he said, adding that it was a confirmed poaching incident. Officials said it was the first poaching case in the UNESCO-listed heritage site in a year. Previous years had seen numerous poaching incidents.

Officials said poaching attempts have increased in and around the park since the start of the nationwide lockdown in late March.

In April, more than five attempts to slaughter the rare creatures were thwarted by park rangers and a special rhino protection force set up by the state government. The one-horned rhinos used to be widespread in the region but hunting and habitat loss has slashed their numbers to just a few thousand, almost all in the northeastern state of Assam.

Their main haven now is Kaziranga, with 2,413 of the animals living there, according to a 2018 count. The 850-square-kilometre (330-square-mile) park, created in 1908 after the wife of the British viceroy visited and complained there were no rhinos, is also home to tigers, elephants and panthers.