An operation was launched in the Agratoli and Kohora ranges of the park since last night and the two poachers were killed at the border of the two ranges, they said.
A group of four poachers had entered from the northern side of the park. On a tip off, an encounter took place between them and forest security personnel, the officials said.
While two poachers were killed on the spot, two others managed to escape.
A .303 rifle and an axe was found on the spot.
Altogether 12 rhinos have been killed in the park since January this year.
The state forest department has stepped up security in and around the park by deploying an additional battalion of Assam Forest Protection Force in the park since last week.