MARSEILLE (AFP) - French police are facing a new form of weapon during "yellow vest" protests - bags of faecal matter thrown bomb-like by demonstrators.

Last Saturday (March 2), "bags filled with faeces were thrown at police and exploded. Three policemen were soaked through with it", Mr Rudy Manna from the Alliance police trade union in the southern port city of Marseille told AFP.

One policeman also suffered an elbow injury when hit by "a poop-filled projectile", Marseille police headquarters said.

Similar incidents took place in the southern city of Montpellier, police trade union representatives said.

Police said there had been calls on social media ahead of last Saturday's demonstrations for protesters to arm themselves with "Caca-tovs" - after Molotov cocktails but filled with "caca", the French term for poo.

"The policemen were deeply humiliated," Mr Manna said, adding that none of the perpetrators, hidden in a crowd of about 1,000 demonstrators in Marseille, had been identified.

Last Saturday marked the 16th straight weekend of "yellow vest" demonstrations in France since November, which have often seen security forces targeted with stones and other projectiles.

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The authorities said nearly 40,000 people took part.

A total of 11 people have died during the demonstrations which began over fuel taxes but mushroomed into a revolt by people in rural and small-town France against French President Emmanuel Macron.