The emergency ministry spokesman quoted by RIA Novosti reported 37 dead, adding that "the exact number of those injured is unknown."

Confusing reports also came as to the number of those rescued from the burning building, with emergency ministry officials saying that "some 100 people were rescued and 50 were hospitalized, there is no threat to their lives, they are safe," as quoted by Interfax.

Earlier firefighting officials said that some 150 people were rescued.

Flames began on the second floor of the eight-story building of Moscow's 17th city drug hospital at 0140 Moscow time (2240 GMT Friday).

Over 20 fire engines were rushed to the site in south-west Moscow, with firefighters managing to stop the fire from spreading an hour later.