Punjab National Bank (PNB) on Friday reported its highest-ever quarterly net profit of Rs 5,532 crore for the September quarter, up 12.8% year-on-year, aided by higher interest income and improving asset quality. Net interest income rose 10.8% to Rs 11,601 crore, while operating profit grew 4.2% to Rs 7,532 crore. The domestic net interest margin (NIM) improved to 2.74% from 2.64% in the preceding quarter, while global NIM rose to 2.58% from 2.50%.