Gabonese striker Henri Antchouet scored a second half hat-trick. Brazilian midfielder Roberto Mendes da Silva had earlier opened the scoring with a penalty in the 29th minute before Lalrindika Ralte made it 2-0.
After the change of ends, ND Opara added his name to the scoresheet before Henri joined the party with a treble.
At the Yuba Bharati Krirangan stadium in Kolkata, Sporting Clube de Goa struck through a penalty to hold hosts Mohun Bagan 1-1.
Syed Rahim Nabi gave the home side a 73rd-minute lead. But in a space of seven minutes, Sporting Clube equalised when Kalu Ogba Nnanna converted a spot kick.
At Thiruvananthapuram, David Sunday scored a brace, including the winner, as Chirag United Kerala defeated Prayag United 2-1.