National Guard troops have taken control of oil distribution centres after President Hugo Chavez ordered them to keep the country's vital industry running.

There are fears that basic commodities will run out

Mr Chavez ordered the crackdown on the eighth day of a general strike which has crippled oil production and led to panic buying and cash withdrawals.

The move came as the head of the state oil company said oil production and exports had been paralysed by the stoppage.

Organisers of the shutdown - designed to force Mr Chavez from office - said it would continue.

International oil prices have risen sharply since the strike began to have an effect on the production of Venezuela - the world's fifth largest oil exporter - last week.

I went to seven gas stations and they were all closed

Johnny Mota, Caracas

Many petrol stations have run out of fuel and there are long lines of cars queuing for pumps which are still open.

Security forces had been sent to oil installations earlier in the strike to guard facilities, but Mr Chavez has now extended their role to guaranteeing supplies and exports by all means necessary.

The Reuters news agency quoted General Wilfredo Silva as saying that National Guard troops had entered the Guatire gasoline distribution plant - which supplies fuel across the capital, Caracas - to secure deliveries.

National Guard troops have also taken up positions at petrol stations and there are reports that tanker trucks have been commandeered.

Striking oil executives say that production, normally three million barrels a day, is down by as much as 90%.

Strike 'goes on'

The head of state oil firm PDVSA, Ali Rodriguez, warned that Venezuela might have to pay a $6bn penalty if it failed to meet its oil export commitments this month.

Industry experts say that even if the strike ended immediately, it could take weeks for oil production to return to normal because refineries take time to restart.

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Click above to see Venezuela's oil export terminals

But Carlos Ortega, leader of the Venezuelan Workers Federation, the country's largest trade union, vowed that the action will continue.

Government opponents want Mr Chavez to submit to a referendum on his rule which they believe would see him have to resign.

"The people you never listened to are going to oust you," Mr Ortega said.

Stoppage spreading

Correspondents say the effects of the strike are being felt ever more widely in Venezuela.

I cannot believe what is happening in my country

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Many schools and businesses in the capital, Caracas, and other major cities remain closed, and domestic airline pilots and aluminium workers are the latest to join the stoppage.

Shops are reporting intense buying of all basic commodities but there are fears that demands for water, food, cash and petrol will exceed supply.

"I went to seven gas stations and they were all closed," said Johnny Mota, waiting with 34 other drivers at a pump in eastern Caracas.

Shopper Luisa de Perez said: "I'm buying lots of canned goods because they can last for months. I hope things are going to get normal, but some products are already starting to run out."

Rally bloodshed

The strikes have also sparked violence. Three people were killed on Friday night when gunmen opened fire at an opposition rally.

Six suspects in the shooting were brought before a judge on Sunday, and all but one - a Portuguese national - have now been released on bail.

Cash machines are being emptied by anxious bank customers

Talks between the two sides - suspended when the strike began - resumed but appeared to make little progress at the weekend.

Mr Chavez - who has warned he may declare a state of emergency if the disruption continued - used his weekly Alo Presidente television programme for a lengthy diatribe in which he dubbed the opposition "coup-mongers".

"They won't rob Venezuela of its happiness," he shouted, grabbing a plastic model of the baby Jesus from a crib on his desk and kissing it before vowing never to stand down.