An immediate investigation has been launched after HMS Ambush was involved in the ‘glancing’ collision while submerged off the coast of Gibraltar, the Royal Navy said.
The Astute-class vessel suffered ‘some external damage’ but no crew members were injured in the incident, which the Ministry of Defence said occurred while it was at periscope depth.
The attack submarine’s nuclear reactor was undamaged.
It is not clear whether both vessels were moving at the time or if one was stationary.
The submarine was involved in the accident despite being equipped with what the Royal Navy boasts are ‘world-leading sensors’.
A statement posted on the MoD website said: ‘HMS Ambush, an Astute-class submarine, while submerged and conducting a training exercise was involved in a glancing collision with a merchant vessel off the coast of Gibraltar.’