The threat to vessels remains small, but the recent fatal attack on an Israeli-connected tanker represents a troubling turn in the so-called "shadow war" between Iran and Israel.

Maritime security consultancy Dryad Global said in a note that the drone attack on the 49,992-dwt tanker Mercer Street (built 2013) on 29 July represents an escalation in the spate of covert attacks on commercial shipping between the two countries, as it resulted in the death of a UK security guard and the tanker's Romanian captain.