By Leigh Thomas and Simon Carraud
PARIS, March 16 (Reuters) - Protesters set fire to a bank and ransacked stores on Paris' landmark shopping street in a new flare-up of violence as France's yellow vest demonstrations against President Emmanuel Macron and his pro-business reforms entered their fourth month.
Police fired tear gas and water cannons as the protests turned violent again after weeks of relative calm during marches and declining numbers of participants.
A branch of Banque Tarneaud spewed flames before firefighters arrived and two news-stands on the Champs Elysees avenue caught fire as bonfires burned in the streets.
Protesters threw cobblestones at riot police through clouds of tear gas in front of Paris' Arc de Triomphe monument, which was ransacked at the peak of the protests in December.
Police had arrested more than 80 protesters by mid afternoon as demonstrators looted stores around the Champs Elysees and ransacked the high-end Fouquet's restaurant.
Interior Minister Christophe Castaner said the protests were small compared with a few weeks ago, with only 8,000 people participating in Paris.
"But within this 8,000, there are more than 1,500 ultra violent people who are there just to smash things up, to fight and to attack," he said, adding more than 1,400 police officers were mobilised.
"I've given instructions to the police this morning for great firmness so that nothing slips by," he added.
Protesters have promised to draw bigger numbers to mark the fourth month since the movement erupted in mid November, over since-scrapped fuel tax hikes and the high cost of living.
Named after the high visibility vests French drivers have to keep in their cars and worn by protesters, the revolt quickly swelled into a broader movement against Macron and his reforms.
However, the weekly demonstrations, held every Saturday in Paris and other cities, have been generally getting smaller since December, when Paris saw some of the worst vandalism and looting in decades.
After the spike in violence, Macron offered a package of concessions worth more than 10 billion euros ($11 billion) aimed at boosting the incomes of the poorest workers and most pensioners.
His government ordered police to crack down on the protests in January, leading to complaints of police brutality after a series of injuries.
The 41-year-old former investment banker also launched a series of national debates which are aimed at determining what polices people want the government to focus on.
Saturday's protests coincide with the end of the debates.
($1 = 0.8829 euros) (Additonal reporting by Emmanuel Jarry; Editing by Mark Potter)
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