Bhubaneswar, Feb 26: A four-wicket haul by debutant Samir Mohanty enabled Orissa register a thrilling four-run victory over hosts Assam in their opening match of the East Zone Ranji Trophy Tournament at Nehru Stadium in Assam on Tuesday. According to reports received here, medium pacer Mohanty`s fine performance was instrumental in restricting Assam to 239 for nine in the stipulated 50 overs. Earlier, Orissa rode on a half-century by Payas Ranjan Sinha, also a debutant, to compile 243 for nine in 50 overs. Orissa will next meet Tripura on February 28. Brief scores: Orissa 243/9 in 50 overs (Payas Ranjan Sinha 50, Shiv Sundar Das 45, P Jayachandra 24, Debasis Mohanty 22, Pritamjit Das 20 n.o; S Suresh 3/36, Krishna Das 3/56) beat Assam 239/10 in 50 overs (S Baruah 59, Sib Sankar Roy 35, Dhiraj Goswami 28, Sanupam Purakayastha 20; Samir Mohanty 4/34) by 4 runs