LONDON, ENGLAND - London-based oil broker PVM Oil Futures said Thursday it had been the victim of 'unauthorised trading", reportedly causing an eight-month spike in the oil price and losing the firm 10 million US dollars.

'PVM can confirm that it was the victim of unauthorised trading on Tuesday 30th June,' managing director Robin Bieber said in a statement.

'As a result of a series of unauthorised trades, substantial volumes of futures contract were held by PVM.'

The firm said the positions were subsequently closed but it suffered a loss 'totalling a little under US$10 million'.

According to the Financial Times, the trade involved up to 9,000 lots - about nine million barrels - of Brent North Sea crude oil which pushed the price to a high of 73.50 on Tuesday.

PVM said it was investigating the trades but did not name any employee suspected of being involved.

'PVM expects the highest standards of conduct from its people and takes contraventions of those standards extremely seriously,' it said.