Gallacher, who finished among the top 10 in the tournament last year, eagled his last hole with a putt from off the green.
"It was a perfect morning," the Scot said. "Cool to start with and then it heated up later on in the round, and not too much wind, so it was perfect."
Suri joined Gallacher at the top when his bunker shot on the 18th hole gave him a birdie.
Suri missed the cut last year in his only appearance at the Indian Open and is playing just his second event of the season after surgery on an abdominal hernia.
"To shoot a score like this, on a course like this, is a good sign going forward," the American said, who made a hat trick of birdies from the seventh.
Karlsson enjoyed eagles on Nos. 7 and 8, and Larrazabal eagled the par-4 13th.