The recent spate in attacks on commercial shipping during the Iran war has increasingly involved supertankers, highlighting the challenges of reviving the region’s oil flows to the global market.

Since a now-shelved peace pact was announced in June, five out of nine attacks on commercial ships were on so-called very large crude carriers, the mainstay vessel type that moves Middle East oil to the world, according to data compiled by Bloomberg from the International Maritime Organization. 

Prior to the peace pact, out of 48 commercial ships that sustained damage in during wartime, nine were VLCCs, including three that had been involved in moving Iranian barrels and were disabled by the U.S. Navy, the IMO’s recap and Bloomberg’s reporting of the incidents shows. 

It may be that the increased proportion of supertankers getting attacked reflects attempts by Middle East oil producers to get more cargoes through the waterway, giving Tehran more of the vessels to target — rather than a new strategy of targeting the vessels. Even so, the incidents demonstrate the risk of transit for vessels that normally dominate the export of Persian Gulf barrels.

The IMO says four of the five supertankers sustained damage off the coast of Oman without specifying exactly where. Separate reporting by U.K. Maritime Trade Operations shows several have taken place in or near Hormuz.

The IMO’s secretary general told Bloomberg Radio on July 15 that ships should continue to avoid navigating Hormuz because of the current level of navigational risk.