"Anguished over the loss of lives at the Kumbh due to heavy rains. May Almighty give strength to the bereaved families to overcome the grief," he tweeted.
"I hope the injured recover quickly. I pray for the safety & well-being of all saints, pilgrims and tourists at the Kumbh," Modi said in another tweet.
At least six people were killed and 40 injured as the Kumbh Mela in Ujjain was hit by lightning and squall, flattening and uprooting pilgrims' tents.