Patrolling forest personnel heard gun shots inside the Burapahar range and launched an operation in the area, park officials said.
A group of about seven militants opened fire and an encounter ensued but the militants managed to escape after shooting the rhino, officials said.
The militants could not take away the horns of the beast, they said, adding that the rhino succumbed to bullet injuries.
Empty cartridges of AK-47 and .303 rifles along with four live ammunition were found near the rhino carcass.
Suspecting the presence of poachers, forest guards had fired in the same range of the park yesterday. There was, however, no injury to any animal or person.