(Bloomberg) -- France’s Yellow Vests should join forces with labor unions to launch strikes and create disruption at companies, the head of the country’s biggest public service union said as the grass-roots movement readies for fresh demonstrations on Saturday.

“The best way to protest is to go on strike ,” the CGT’s Philippe Martinez said on Friday on BFM TV. “We must multiply actions at companies. We must strike everywhere.”

His call to shift protests from streets to production lines ahead of a fifth Saturday of demonstrations comes three days after a deadly attack at a Christmas market in Strasbourg raised security concerns. Police killed the assailant late on Thursday.

Dented Economy

On Monday, Macron unveiled a 10 billion-euro package of economic and social measures, including a 100-euro monthly bonus for minimum wage earners paid by the state.

Previous protests have seen violent clashes between rioters and police, torched cars, looting, and broken windows in the French capital, hitting retailers and the tourism industry in the run up to Christmas, and denting the French economy.

Paris police chief Michel Delpuech said he expected further potential violence this weekend. Authorities were making preparations with extra riot police -- 8,000 in Paris -- and four tank-like vehicles to protect sensitive landmarks including the Elysee presidential palace.

French Interior Minister Christophe Castaner said on Friday that the demonstrations were facilitating violence by members of the extreme left and right, and looters.

“Apparently there will be an Act 5 in the Yellow Vests protests tomorrow in Paris,” he said in an interview with Europe1 radio. “I would prefer an act of responsibility. For our police, for our storekeepers, for our economy.”

People across France have been pulling yellow vests from the trunks of their cars for more than a month to express a whole series of grievances. What began as traffic blockades has peaked in serious violence in Paris for the past two weekends. Yet the only thing the protesters really have in common is their anger toward President Emmanuel Macron. The lack of a single policy goal means at least some protests are almost certain to continue.

Terror Threat

Police forces, who’ve also been deployed to address tensions in some high schools and universities, now have to add terrorism to the equation. French authorities increased the national terror alert to its highest level after the shooting in the streets of Strasbourg on Tuesday. Three died, with a dozen wounded.

“Law enforcement could be significantly distracted because of the recent terrorist attack," Ryan DeStefano, vice president of security for travel risk management provider On Call International, said in an emailed note. “In addition, protests provide an opportune time for radicals to engage in terrorist activities under the guise of peaceful protest.”

At least one union head, Laurent Berger of the CFDT union, called for a halt to the Yellow Vests demonstrations. Some members of the movement have urged to end street protests and focus instead on road blockades.

To contact the reporters on this story: Helene Fouquet in Paris at hfouquet1@bloomberg.net;Geraldine Amiel in Paris at gamiel@bloomberg.net

To contact the editors responsible for this story: Ben Sills at bsills@bloomberg.net, James Regan, Angeline Benoit

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