This study will be performed to compare the efficacy and safety of the classical "Step-Up" approach for treatment of moderate-to-severe active ulcerative colitis using oral prednisolone + oral 5-aminosalicylic acid (5-ASA) or oral prednisolone + oral azathioprine (AZA) with a more intensive and early "Top-Hold" approach with intravenous infliximab (5 mg/kg) administered at Weeks 0, 2, and 6 and 8 weeks thereafter.