These rules have developed over centuries as states sought to regulate the conduct of conflict at sea while still allowing navies to operate effectively.

The reported sinking of the Iranian warship IRIS Dena by a US submarine using a Mark-48 torpedo in the Indian Ocean has triggered debate among military lawyers and analysts about whether the strike was lawful under international law.

The sinking of an Iranian warship by a US Navy submarine off the coast of Sri Lanka this week is something a US sub hasn’t done in more than 80 years and is another indication that Washington’s war with Tehran is taking on a breadth also not seen in decades.

Iran condemned the attack on the Iranian vessel that led to the killing of 87 sailors and claimed that it was unarmed and unloaded when it was sunken by the US.

An Iranian ship had been invited by India to take part in peacetime naval exercises with dozens of other countries, days before it was sunk in a U.S. submarine attack.

The Pentagon has released footage of the moment a U.S. submarine sank an Iranian ship with a torpedo in the Indian Ocean on Tuesday.

Tensions rose in Sri Lanka after Opposition MP Mujeebur Rahman revealed that the Iranian warship IRIS Dena waited 11 hours off the southern coast. The ship was then sunk by a US submarine, killing 87 sailors.

Iran Navy ship Iris Dena was on its way back home after taking part in a naval exercise organised by India when it was struck by US submarine attack on March 4.