Spain on Friday offered a rebate and a onetime cash payment to end a truckers' strike over soaring fuel prices that has led to food shortages in supermarkets nationwide.

But the main trucker group behind the protests rejected them as insufficient and vowed to keep up its work stoppage.

The government offer includes a rebate of 0.20 euros ($0.22) per litre of fuel and a onetime 1,250-euro payment per truck, Transport Minister Raquel Sanchez told reporters, adding that the total cost to the state would be around one billion euros.

"The vast majority of truckers want and need to work. With this agreement we are offering them the possibility to do so," she said after talks with transport associations which represent the bulk of the sector.

Drivers and truck owners belonging to a group called Platform for the Defence of Transport have since March 14 been blocking roads and ports to draw attention to the rise in fuel prices, fuelled by Russia's invasion of Ukraine.

The strike has disrupted supply chains in several industries and caused sporadic shortages of perishable foods such as eggs and dairy products in the eurozone's fourth-largest economy.

The group, which did not take part in the talks with the government, swiftly rejected the measures.

Sanchez finally agreed to meet its leader on Friday afternoon, but he stood firm.

"We will continue with this open-ended strike," the platform's president, Manuel Hernandez, said.

"If it costs us money to work and nothing is done about it, we can't work," he added.

Waving Spanish and regional flags, thousands of the group's supporters marched on Friday morning along La Castellana, one of Madrid's main avenues, blocking traffic.

Like many self-employed truckers, Jose Luis who came to the protest from the nearby city of Toledo, said what he is being paid for hauling loads does not currently cover his costs.

"If I have to put money into my business, my truck is staying home," he told AFP.

The strike has disrupted the supply chain in many industries
The strike has disrupted the supply chain in many industries AFP / Pierre-Philippe MARCOU

The rebate offered by the government is not enough "because in a few months fuel prices will rise again," he added.

Hernandez earlier dismissed the government aid as "crumbs".

He said fuel prices would have to drop by over 0.60 euros per litre to cover truckers' costs and demanded higher payments to transport freight.

"You can't pay people who are performing a service less than their operating costs, that is the problem that must be limited," he said during an interview with Spanish public radio.

But the president of the country's main trade association of hauliers, Carmelo Gonzalez, said his group was "satisfied" with the measures and he hoped the strike would now end.

"It would be incomprehensible if the blockades continued," he said.

Several major firms such as Dutch brewer Heineken and French giant Danone have had to suspend production because of a lack of raw materials.

Taxi drivers, farmers and fishing crews have also protested in recent days against rising fuel prices, sometimes setting up temporary barricades to block traffic.

The government aid will apply to other transport companies, including bus and taxi drivers who will receive smaller one-off payments.

The fuel rebate will come into effect on April 1 and last until June 30, and could be extended further if needed, the government said in a statement.

A quarter of the rebate will be covered by energy companies, it added.

Transport associations had rejected a 500-million-euro aid package offered by the Socialist Prime Minister Pedro Sanchez's government on Monday.

The government has mobilised thousands of police officers to help keep traffic moving by escorting truck drivers who are not taking part in the strike.