The protesters prevented other lorries from passing, and caused delays to car traffic.
Hundreds of lorry drivers also staged "snail protests" on the ring roads around the capital, Madrid, and Barcelona. There have also been protests in the Basque country and Valencia.
Petrol stations around Madrid and in the north-eastern Catalonia region are already said to be running short of fuel.
Most of the 90,000 hauliers participating in the strike are self-employed, or working for small and medium-sized haulage companies, and they have warned that many supermarkets will run out of goods within days.
"We are the ones who move the goods that this country needs to keep working," the head of the transport association federation Fenadismer, Julio Villascusa, told Cadena SER radio.
"If we stop because we haven't got the money to buy fuel then the country will stop."
Spanish hauliers' fuel strike
The president of another drivers' trade union, Adetec, said many of its small-scale hauliers were going bankrupt.
"We have no more solutions. We can't afford diesel any more. It's as simple as that," Jean-Claude Ferrand told Spanish national radio.
The lorry drivers are receiving support from counterparts in Portugal and southern France, who also disrupted the flow of traffic along one of the main routes into Spain.
However, Spain's largest hauliers' trade union is not taking part.
EUROPEAN FUEL PROTESTS
Belgium: Fishermen clash with police at protest near EU on 4 June
Bulgaria:150 lorry drivers form convoy outside Sofia on 28 May
France: Lorries and taxis block motorway in Paris on 3 May in support of strike by fishermen
Italy: Fishermen on both coasts begin strike on 30 May
Portugal: Portuguese fishermen stay in port on 30 May
Spain: Spanish fleet begins strike on 30 May. Madrid fishermen hand out 20 tonnes of free fish to public
UK: Truck drivers block London roads on 28 May. Fishermen hold mass protest in capital on 3 June
The drivers want the Spanish government to establish, by law, a minimum price for their services, and to ensure that haulage contracts better reflect the fluctuating cost of fuel, which has risen by more than 20% since the start of the year.
But the BBC's Steve Kingstone in Madrid says that with inflation at an 11-year high, the government is reluctant to approve a minimum price for the work of lorry drivers - fearing that the additional costs would immediately filter through to other sectors of the economy.
Instead ministers are proposing a mixture of short-term funds and long-term restructuring for the haulage industry.
On Monday the government said there was a "reasonable chance" of a deal by midweek, our correspondent reports.
The hauliers' action follows the lead of Spanish and French fishermen, many of whom have been on strike because of the soaring price of fuel.
The fishermen have said they will go out of business unless the EU allows national governments to give them more financial aid and subsidise maritime diesel.
However, the EU has insisted that any fuel subsidies would be illegal under European law and unsustainable in the long term.
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