Doctors at the Lilavati Hospital in suburban Bandra performed a life-saving surgery on him, hospital sources said.
Singh (70) is under observation and is stated to be in critical condition, they said.
He was to perform at a concert in Mumbai on Saturday
Later, a close family friend told reporters at the Lilavati hospital that the singer was operated upon for removal of a blood clot in his brain.
He claimed that the singer was out of danger "but will be kept under observation in the ICU for the next 24 hours".
Image: Jagjit Singh