Oil production in Venezuela has plummeted to a quarter of its normal levels as an open-ended general strike wears down the world's fifth-biggest producer.

People queued at banks to withdraw cash, or were panic-buying at petrol stations and supermarkets, as the strike continued into its ninth day on Tuesday.

The United States has issued a travel warning to its citizens and allowed non-essential Embassy staff to leave the country, citing the "deteriorating political and security situation".

Mr Chavez is a left-over Communist who wants to destroy his country

Gualterio Bamberg, Caracas, Venezuela Are you affected? Click here to have your say

Venezuela's defence minister has made an impassioned appeal to stop the strike, which the opposition hopes will lead to a referendum on President Hugo Chavez's rule.

"Fellow Venezuelans, let us get back to normal quickly, because otherwise the market will be taken away from us," Jose Luis Prieto said on TV.

He said that Mexico was ready to take Venezuela's place in the oil market otherwise.

International efforts to mediate between President Chavez and the opposition faltered after initial progress on discussing new elections.

"I can't say we've advanced," said Cesar Gaviria, Secretary-General of the Organisation of American States, after the latest round of talks.

Heavy losses

The head of the state oil company PDVSA, Ali Rodriguez, announced on Tuesday that the country's largest refinery, Paraguana, had shut down.

Paraguana normally processes three-quarters of the country's oil.

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Click above to see Venezuela's oil export terminals

Energy Minister Rafael Ramirez said that the country was losing $50m a day in oil exports.

But, the BBC's Nick Miles reports from Caracas, the opposition is in no mood to back down and has been celebrating the anniversary of the first national strike, one year ago, against President Chavez.

The opposition Democratic Coordinating Board said the strike would continue "ever stronger and fearless".

Venezuela's Supreme Court announced that it was suspending all but essential work, accusing the government of "harassment and insults".

Travel warning

The United States issued its travel warning days after three people were shot dead and 28 wounded at an opposition rally.

Some media outlets have been trashed by Chavez supporters

The State Department warned citizens to postpone travel to Venezuela and urged anyone already there to consider departing.

But leaving the country could be difficult as the country's main airline has been grounded by the strike.

"It looks like a cold civil war in which each side is sitting in its trenches, but the situation could explode at any moment and turn into a real civil war," one political analyst, Alfredo Keller, told the French news agency AFP.