A fire has killed has killed at least 35 people at a private hospital in the eastern Indian city of Kolkata.

Authorities say the blaze swept through the AMRI Hospital early Friday in the capital of West Bengal state.

Local television channels showed patients being rolled out on stretchers and distraught relatives waiting outside the hospital as smoke engulfed the multi-story building.

Rescuers broke windows to get to some of the patients who were trapped and later moved to a nearby hospital.

Officials say the fire broke out in the hospital's basement, where chemicals were stored.

Firefighters worked to bring the blaze under control and rescue those still trapped inside the building.