At least four petrol stations in Oxfordshire ran dry yesterday as hundreds of tanker drivers prepared for a fourth day of strikes.

Other filling stations around the county also ran low on stocks as motorists hit the pumps in the face of the industrial action and the threat of more to come.

Members of the Unite union employed by two companies which makes deliveries for Shell are due back at work tomorrow after a four-day walkout over pay.

But a potential second strike later this week left garage managers wondering whether there would be enough time and resources to stock up and fearing panic buying - which had so far been minimal - could escalate.

Of the ten Shell petrol stations in the county, four have no unleaded petrol and diesel until tomorrow at the earliest.

They are at London Road, Oxford; Broadway, Didcot; London Road, Bicester; and Chapel House Crossroads, Chipping Norton.

Tony Hallan, who manages the Shell petrol station in London Road, Headington, said initially he had expected to have enough fuel until Tuesday, but pumps ran dry yesterday morning.

He said: "It's a bit of a nightmare. In the end, motorists were panic buying.

"People hear it on the radio, they watch it on the TV and they read it in the paper - the general public think they need fuel.

"Now the drivers claim they are going to go on strike again. The system won't be able to catch itself up - that alone will take three or four days."

Trading supervisor Sohail Dogar added: "It's really affected our sales because customers tend to buy from the store when they buy petrol - the sooner we get fuel, the better."

Meanwhile, Shell's Frilford Service Station in Marcham Road, Frilford, is rationing fuel in a bid to see out the strike.

Sales assistant Ryan Wall said: "We are selling a certain amount each day to try to be as fair as possible to everybody and make sure there's some for the emergency services as well.

"There are a few people who have filled their cars right up and a couple of people have come in with petrol cans, but it's mostly been steady trade."

Despite reports some non-Shell stations had struggled to keep up with demand, many reported only a slight increase in sales as the majority of motorists heeded advice not to panic buy.

Prabar Subramanaam, a supervisor at the Q8 petrol station in Cowley, Oxford, said: "People have been buying more petrol, but we have plenty."

Don Ezason, manager of Shell's Barrington Filling Station, near Burford, added: "It's been a little busier, but we haven't had any queues.

"But if one of two stations run dry, then people might start to panic - and we don't know the impact of next weekend."

Nationally, 647 Shell stations were said to be affected. The Government has urged people not to panic buy fuel and for both sides to resolve the pay dispute as soon as possible.