At least six people were killed in a fire that ripped through a hotel in eastern India on Thursday, police said, with rescue teams still searching the wreckage for survivors.

The fire broke out at the Pal Hotel in Patna, the capital of Bihar state, and soon spread to adjacent buildings before it was extinguished.

"So far six people have been killed," a police officer told AFP on condition of anonymity, adding the toll was likely to go up as the rescue operation was still underway.

At least 18 others were injured and were "battling for their lives" in a local hospital, the officer added.

It took more than three hours for firefighters to extinguish the blaze, which began around noon.

Senior fire brigade officer Sobha Ohatkar said negligence had likely led to the disaster.

Fires are common across India because of poor safety standards and lax enforcement of regulations.

Many commercial buildings lack emergency exits or functional fire-fighting equipment.