Forest officials suspect the tiger strayed from the Oranga National Park and swam to the island.
A royal Bengal tiger swam 120 km across the river Brahmaputra to a tiny island before it was tranquilised after a 10-hour effort and moved to the state zoo.
In a video that is viral, the tiger is seen speed-swimming in the Brahmaputra and then hiding in a narrow cave on the Peacock Island near Guwajati that is famous for the ancient Umananda temple.
A group of workers at the temple were stunned on Tuesday morning when they saw the tiger swimming towards what is the world's smallest inhabited island.
The tiger was seen swimming towards a narrow cave on the island that draws scores of devotees every day.
Forest officials suspect the tiger strayed from the Oranga National Park located about 120 km from the island, which is a 10-minute boat ride across the Brahmaputra from Guwahati city. The animal was possibly swept away by the strong currents of the Brahmaputra while drinking water.
Amid panic among people on the island, a unit of the National Disaster Response Force (NDRF), which has a base nearby, was alerted, along with the local police. Forest department officials and a rescue team, including veterinarians, rushed to the spot in boats.
The teams found it difficult to tranquilise the tiger as it was at a distance from the riverbank. "The tiger was stuck between two large rocks and the rescue team had to carry out the operation very cautiously," said an official quoted by news agency PTI.
It was a hard task as if anything went wrong, the tiger could have fallen back into the river and drowned. If it was not tranquilised fully, it could attack members of the rescue team.
"After the team was sure that the tiger has been fully tranquilised, they proceeded to rescue and capture it and put the animal into a cage. This took considerable time as the space between the rocks was very narrow," the official said.
Ferries full of devotees headed to the Umananda Temple were evacuated as forest officials surrounded the river island and managed to tranquilise the big cat.
Priests were also moved to safety and shops and establishments catering to temple visitors were also shut down briefly as officials tried to surround the tiger.
The Umananda Temple was built by the Ahom King Gadadhar Singha in the last decade of the 17th century.