Lloyd's said that the Gulf, part of the Gulf of Oman, Oman and the United Arab Emirates had been added to the list. Saudi Arabia's risk areas were meanwhile expanded to include its coasts.
It comes after marine insurers in London began Thursday an extraordinary meeting to discuss the situation in the Gulf.
The meeting was of the Lloyd's Market Association (LMA) Joint War Committee, which normally gathers on a quarterly basis to assess security risks to shipping around the world.
"The London insurance market's Joint War Committee (JWC) has been considering developments in the Gulf," Neil Roberts, head of marine and aviation at the LMA, which represents all underwriting businesses on the Lloyd's of London insurance market, said in a statement Friday.
"In the light of further information received, the JWC has today issued this advisory notice to the market, amending the listed areas which detail areas of perceived enhanced risk for marine insurers and reflecting the enhanced regional risk."
It follows insurgent drone strikes on a key oil pipeline in Saudi Arabia and the mysterious sabotage of four ships, including two Saudi oil tankers, earlier this week.
The attacks have escalated tensions between the U.S. and Iran but industry analysts have questioned the exact circumstances of the ship attacks.
Lloyd's List Intelligence, a business information service, earlier this week said there had been "scant information" about the incident from Saudi authorities.
"Saudi reticence to report the incident accurately within their own media channels and the current failure to provide imagery evidence of the attack raises important questions as to the nature of the attack," maritime security company Dryad Global told clients in a note, Lloyd's List said.
Attacks on Saudi and UAE oil assets built to bypass the Strait of Hormuz, a strategically important waterway in the Gulf, have raised fears that alternative routes could be vulnerable.
Four ships including two Saudi oil tankers were damaged in mysterious sabotage attacks Sunday off Fujairah, an emirate located at the crucial entrance to the Gulf.
That incident was followed by drone strikes Tuesday by Yemen's Huthi rebels on a major Saudi oil pipeline, which provided an alternative export route if the Strait of Hormuz closed.