Oil prices hit record levels once more today as fresh threats to Yukos production, scepticism over Opec pledges of extra output and concern over the effects of a refinery fire in the US sent the cost of crude soaring.

In New York the cost of US light crude hit $44.77 a barrel, the highest level in the 21 years since oil trading was revamped, before easing a little.

In London Brent crude touched $41.50 a barrel, its highest level in 16 years of trading on the International Petroleum Exchange.

Reports said that the Russian authorities had seized $900 million from Yukos, leaving the Russian oil giant, which produces nearly 2 per cent of the world's oil, facing a cash crunch that could halt production.

"All revenues coming into our bank accounts are immediately transferred (by bailiffs) to the public exchequer. As of Thursday a total of $900 million had been written off. It is definitely a threat to our operations," a Yukos source told Reuters, the news agency.

Russia's Justice Ministry yesterday revoked permission granted by bailiffs for Yukos, which owes £3.6 billion in back taxes, to tap frozen accounts for cash to keep operations running. Some observers feared that the u-turn could, by the end of the week, force Yukos to shut down rail shipments needed to secure a quarter of its exports.

"The outcome lies in the [Russian] government's hands. Prices will remain at high levels until there is some kind of resolution," said John Bates, an analyst at WestLB.

Meanwhile, Purnomo Yusgiantoro, the president of Opec, the oil producers' cartel, said that the organisation's 11 members were exceeding their current quota limits by 2 million barrels a day and were operating close to capacity.

The announcement looked to conflict with statements from Opec officials over recent days which suggested that Opec could pump another 1.5 million barrels of oil a day to calm the markets.

Mr Yusgiantoro today said that any hike in output from Yukos would not happen until September at the earliest.

"This issue will be discussed in the September 14 meeting in Vienna," he said.

Oil prices had earlier rushed to fresh record highs after a fire at a US refinery fire aggravated market jitters heightened by the Yukos crisis.

The increases followed a blaze at a BP refinery in Texas. While the fire was quickly extinguished, it exacerbated fears over a global shorage of refinery capacity.

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