Protesters in France are angry about an increase in diesel tax, justified as an anti-pollution levy by the government

A wave of protests in France over fuel prices and low living standards has spilt into neighbouring countries, causing disruption for truckers in Britain and Spain and leading to arrests in Belgium.

Several dozen people were detained at a fuel depot in Belgium near the French border overnight Wednesday-Thursday, while Spain slammed traffic jams on the border with its northern neighbour.

Hundreds of thousands of people wearing fluorescent yellow jackets began blockading roads and energy infrastructure across France on Saturday to protest against higher fuel prices and low living standards.

Road blocks and brief border closures caused traffic jams of some 11 kilometres (seven miles) on Tuesday on the main highway through the Pyrenees mountains between France and Spain, the Spanish foreign ministry said Thursday.

The movement was "obstructing the free circulation of goods between member states" of the European Union, a statement said, adding that the cost was estimated at two million euros.

"The fruit and vegetable sector is particularly affected due to the perishable nature of the goods," it added.

The Spanish government has made an official protest to French authorities, and has also notified the European Commission.

Although the number of protesters in France has fallen dramatically since the weekend, isolated incidents continued Thursday ahead of another national day of action planned for Saturday in Paris.

Around 30 protesters slowed down traffic on the A16 motorway near the Channel tunnel in northern France on Thursday, which is used by thousands of trucks arriving daily from Britain.

Elsewhere in France, President Emmanuel Macron vowed an "uncompromising" response to violence on the island of Reunion which has been hit by riots that began on the sidelines of the protests on Saturday.

Reunion, off the coast of southeast Africa and home to 850,000 people, is experiencing its worst wave of violence in nearly 30 years.

"What has happened since Saturday on Reunion is serious. We have made resources available and we will continue to do so," Macron wrote on Twitter late on Wednesday, adding that paramilitary police would be deployed.

"We will be uncompromising because we can't accept the things we've seen," he added.

Police reported that the number of clashes Wednesday night in Reunion had fallen compared with earlier in the week, with 16 new arrests taking the total to 123 since Saturday.

The "yellow vest" movement -- named after the protesters' jackets -- represents a major challenge for Macron, a 40-year-old centrist who came to power in May 2017 promising to tackle high unemployment and cut taxes.

burs-adp/cb/bp