GUWAHATI, May 27 ? The National Assessment and Accreditation Council (NAAC), an autonomous institution of the University Grants Commission, accredited three universities of the north-eastern region on May 15. These are Dibrugarh University, Tripura University and Arunachal University, a PIB release today said. Dibrugarh and Arunachal universities have been graded ?B? under the new grading pattern and Tripura University has been conferred with a C+ grading. With this, NAAC has so far completed the assessment and accreditation of 261 institutions.