Thirty-seven people have been killed in a fire that swept through a wooden psychiatric hospital in north-west Russia, in the latest tragedy to hit the country's mental health institutions.

The fire early on Friday was started by a patient who was either smoking or deliberately set fire to his bed at the hospital in the village of Luka, 220 kilometres south-east of Saint Petersburg, officials said.

Fatal: Emergency workers and firefighters work at the site in Luka, north-west Russia. Credit:AP

The institution was made out of wood and officials said it had been previously warned by the judicial authorities to improve its fire security.

A criminal probe has been opened into suspected negligence.