The periscope of Indian Navy's submarine INS Sindhughosh was damaged after a fishing boat hit it during an exercise off Mumbai coast, a naval official said Sunday.

"In a minor incident off the west coast, a fishing vessel has hit the periscope of the submarine which was involved in an exercise," the Navy official, adding the incident occurred happened in the night between Thursday and Friday. "The exercise was being conducted in pitch dark conditions as required by the exercise prerequisites," he said.