US President Donald Trump’s administration has fired another volley of sanctions at the so-called shadow fleet serving Iran, sanctioning a swathe of tankers and, for the first time, the tugs that serve them.

The US Treasury added 10 tankers and several associated companies to its sanctions list, and it blacklisted Iranian petroleum minister Mohsen Paknejad.

But it is the state department’s move against three tugs that added a new dimension to the latest round of sanctions.