Oil company BP said it was investigating possible impropriety after a whistleblower sent a letter making serious allegations to Chief Executive Bob Dudley.

We received a letter last week that contained serious allegations, and, as we always do with such matters, we will investigate them, a spokesman said.

Details of the probe were earlier reported in The Daily Telegraph newspaper, which said they related to the company's tanker chartering division and that a copy of the letter was also sent to the Serious Fraud Office.

The shipping market was abuzz with chatter about the matter on Thursday.

The investigation looks like it's happening on a pretty high level, a shipping source said.

Western oil companies say they have devised strict procedures to ensure employees do not engage in offering or receiving improper inducements for business.

Nonetheless, their size and the fact they operate in many countries with weak legal systems, means transgressions are not uncommon.

BP said last year that it dismissed 552 people for non-compliance and unethical behavior in 2010.

(Reporting by Tom Bergin and Jonathan Saul; Editing by Will Waterman)