Hundreds of thousands of Indian pilgrims have begun packing an island in the Ganges for a vast religious festival as Covid-19 cases surge nationwide, prompting fears of a superspreader event.

Officials said they expected as many as three million people, including ash-smeared, dreadlocked ascetics, to take a ritual dip in the holy river on Friday, the climax of the annual Gangasagar Mela.

The state government appealed to people to get tested for Covid-19, with West Bengal Chief Minister Mamata Banerjee urging devotees to wear two masks and not “spit on the island, as it spreads the virus”.

“It's a big challenge amid the raging surge of the Covid variant to maintain social distancing,” local district magistrate P. Ulganathan told AFP.