The United States’ sinking of a “prize” Iran warship off the coast of Sri Lanka suggests tankers carrying sanctioned Iranian oil that sail through busy Southeast Asian waters may not be safe either, analysts say.
While Iranian warships do not make frequent visits to the region, actors looking to disrupt Iran’s income sources could target and destroy this “shadow fleet” of tankers instead, potentially creating environmental disasters and tension with coastal states in the Association of Southeast Asian Nations (ASEAN), the experts add.
For instance, the US could target commercial tankers in a military operation if Washington declares they are not being used for commercial purposes but are believed to be serving Iran’s military aims instead.
CNA reported last December that wars in Ukraine and the Middle East have pushed more of these shadow fleets of tankers into the region, according to observers. These ships carry oil from sanctioned Iran, Russia and Venezuela and transfer cargoes in the Singapore Strait to avoid detection.
They often use stolen identities and other tactics to hide their activities and evade scrutiny. Some may repaint their hulls, change flags and adopt new names to imitate legitimate ships and blend into surrounding traffic.
In 2023, Indonesia seized an Iranian-flagged supertanker suspected of being involved in the illegal transshipment of crude oil, after it spoofed its automatic identification system to show its position was in the Red Sea instead of in Indonesia’s Exclusive Economic Zone (EEZ).
According to experts, the US could also lawfully target Iran-linked merchant ships far beyond the Middle East combat theatre, if it can prove these vessels were being used for military purposes.
On Mar 4, a US submarine torpedoed the Iranian frigate IRIS Dena, with about 130 sailors on board, around 20 nautical miles off Sri Lanka’s southern coast. At least 87 crew members were killed, said officials from Sri Lanka, which conducted a rescue operation.
Iran said on Mar 8 that 104 crew members were killed and 32 others injured.
“An American submarine sunk an Iranian warship that thought it was safe in international waters. Instead, it was sunk by a torpedo,” US Secretary of War Pete Hegseth told reporters in Washington, calling the target Tehran’s “prize ship”.
The incident marked a dramatic expansion of the war and raised questions about the legitimacy of such a strike, including how it has impacted coastal states’ authority in their own backyard.
The United Nations Convention on the Law of the Sea (UNCLOS) defines a state’s territorial waters as extending up to 12 nautical miles (22.2km) from its baseline, with its EEZ extending up to 200 nautical miles immediately offshore.
While coastal states have resource rights in their EEZs, other states retain navigational freedoms. This means coastal states are not allowed to block Iranian or US ships from passing through.
If the Middle East conflict spreads to live strikes in the waters of Southeast Asia, regional bloc ASEAN could issue a statement condemning the move depending on where exactly it took place, although not much more especially if a major power like the US is involved, the analysts told CNA.
