No one was injured in the incident involving the submarine Tireless and there was no radioactive risk, a spokeswoman for the ministry said.

"She's going to Faslane (navy base in Scotland) for a full damage assessment," the spokeswoman said, without giving details on when the incident occurred and whether the object the sub collided with was an iceberg.

The vessel was "submerged and hit a free-floating object", she revealed.

"Why this happened is a matter for the board of inquiry. These submarines have electronic sensor equipment and sonar on board which help in sensing objects."

WAR.WIRE