The flight was operated by Indian carrier Vistara and had 147 people on board.
Police said the bomb threat had been communicated in an online post on X, formerly Twitter, according to DW.
The authorities deployed police teams, complete with explosive detection dogs, to search of the plane after it was evacuated. No explosive device was found on board.
It was not clear when the plane would continue its London trip.
The news of the Vistara plane makes emergency landing comes a day after Indian police arrested a minor in Mumbai on suspicion of him making bomb threats online.
Several Indian airliners have recently received multiple threats via social media. All of them turned out to be false alarms.
On Friday, India's Aviation Minister Ram Mohan Naidu Kinjarapu said "hoax bomb threats have been traced to minors and pranksters."
SD/