Oil prices have fallen further below $50 a barrel as, with the result of the US presidential elections still difficult to predict, traders cashed in positions.

The price of benchmark US crude hit $49.75 a barrel this morning, $0.38 below its closing price last night. The price yesterday briefly dripped below $50 for the first time in four weeks.

Brent crude, which lost nearly $2 a barrel yesterday, stood a further $0.26 lower at $46.80 a barrel.

Analysts said that the declines reflected uncertainties over the outcome of today's US presidential elections, with George Bush and John Kerry neck-and-neck in the polls.

Some analysts believe that a victory for Mr Kerry would spell lower crude prices.

The Democrat candidate has promised to halt a process of filling US oil reserves at historically high prices, freeing more crude on to the market. Some observers also believe that a return of Mr Bush to the White House would stoke nervousness about US policy in the Middle East, where Mr Kerry is viewed as more likely to favour diplomatic channels.

"Kerry is bearish [for oil prices] in a number of ways," David Thurtell, at Commonwealth Bank of Australia in Sydney, said.

Adam Sieminksi, the Deutsche Bank analyst, said: "If [Mr Kerry] wins then there are stronger fuel efficiency drives on the horizon."

Simon Wardell, a World Markets Research Centre analyst, added: "There might be some price bouncing around after the [US presidential results] are released."

Oil prices have also been held back by forecasts of a mild start to winter in eastern states of America, with last week's data showing US supplies at 283.4 million barrels, twice the level the market had expected, continuing to deter buyers.

However, a further setback to Yukos, which is believed to have had its total bill for back taxes raised to $17.6 billion, and the prospect of unrest in Nigeria, where unions protesting at high fuel prices and have condemned Shell as "an enemy of the people", have kept traders on edge.

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