Shares in Yukos slumped by 20 per cent in early deals after bailiffs seeking assets to meet a bill for back taxes said they had seized the oil giant's main production facility. This is the second time that the court officers have taken such action.

Yukos stock had gained 17 per cent yesterday on a court ruling that bailiffs pursuing £1.8 billion in taxes owed for 2000 had acted illegally in seizing the company's Yuganskneftegaz subsidiary. The ruling represented one of Yukos's few victories in its battle against a Government onslaught which has threatened the company with collapse and a break-up of its assets.

However, the Justice Ministry late last night said that "new circumstances" – a dearth of funds in Yukos accounts – had rendered the court decision invalid.

"A court bailiff issued an order arresting its shares in Yuganskneftegaz," the ministry added.

Yukos stock stood 15.4 per cent lower in afternoon trade in Moscow.

Yuganskneftegaz is responsible for about 60 per cent of Yukos's oil production and is viewed as crucial to the group's future. The Yukos crisis has also fuelled the rise in oil prices, which hit fresh record highs last night after sabotage threats brought Iraqi production to a halt.

Benchmark US crude hit $44.99 a barrel with Brent crude reaching $41.70 a barrel.

However, oil prices fell back today, with US crude standing at $44.66 a barrel and Brent slipping to $41.36 a barrel.

A New York-based broker told Reuters: "We need some major new news [for US crude] to break through $45. You'd have to be very brave to buy at $45."

Kevin Blemkin, the GNI-Man Financial trader, said: "We are looking for a dip in prices to about $41.10 [in benchmark US crude], and then a little more buying to come back in."

Oil traders believe that, barring unforeseen events, the short-term direction of the market is likely to be determined by data tomorrow on US fuel inventories.

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