At least three Indian oil refiners and a global energy major plan to stop using vessels on Iran’s new blacklist, including for ship-to-ship transfers, due to security concerns, four sources with direct knowledge of the matter said this week, Reuters reports.

Tehran announced on Sunday a blacklist of 45 ships it said had broken its rules for crossing the Strait of Hormuz, and would take action against any vessels transferring loads with them.

Iran’s announcement appears designed to impede the so-called shuttle runs Gulf oil producers such as the UAE and Saudi Arabia have undertaken with dedicated tankers to move oil from the Gulf through Hormuz for unloading through STS transfers in the Gulf of Oman onto ships to end-users.

“We will avoid our chartered vessels dealing or STS or anything to do with non-compliant ships for Middle Eastern cargoes,” said one of the sources, who works at an Indian refinery.

The sources declined to be identified because of the sensitivity of the issue.