Image copyright OW Bunker

The world's largest ship fuel supplier, OW Bunker, has filed for bankruptcy after alleged fraud.

The company's troubles came to light earlier this week when it discovered suspected fraud by senior employees in a Singapore-based subsidiary.

OW Bunker is Denmark's third-largest company and supplies 7% of the world's bunker fuel, used in shipping.

Shipping lines were trying to find alternative suppliers in the wake of the news late on Friday.

The company owes 13 banks $750m (£472m) and says it cannot survive without new credit.

OW Bunker's chairman, Niels Henrik Jensen, said in a statement: "It is now clear that such facilities will not be made available. Nor is a sale as a going concern a realistic option."

The bankruptcy filing was lodged in the probate court in Aalborg in northern Denmark.

The company said on Thursday it had discovered fraud by senior employees in its Singapore-based subsidiary, Dynamic Oil Trading.

The statement also said: "As a result of the internal investigation it has been decided to report two key employees in the Singapore-based subsidiary Dynamic Oil Trading (DOT) to the police... and to relieve them of duty immediately."

OW Bunker only became a public company this year when it joined Copenhagen's Nasdaq in March. Its float was a market highlight, the second biggest initial public offering of shares since 2010.

In October it published figures estimating a trading loss of $24.5m, but has now increased that to $150m.

The alleged fraud at DOT is potentially one of the biggest financial market scandals to hit Singapore in 10 years.