The French government yesterday accused radicals of storming a famed Paris hospital during a fiery May Day in an incident that risks further raising tensions between authorities and "yellow vest" protesters.

Doctors at the Pitie-Salpetriere hospital, where Diana, princess of Wales, died in 1997 after a car crash in Paris, also said protesters forced their way into the hospital, caused damage and even tried to enter an intensive care unit. But supporters of the yellow vest movement, whose protests have shaken the government of President Emmanuel Macron over the past six months, insisted the demonstrators were merely seeking refuge from tear gas fired by police.

The incident came during a hugely tense May Day that saw Paris police clash with hard-line protesters. More than 30 people were arrested for entering the hospital, Paris prosecutors said.

The tension was palpable as a mix of labor unionists, yellow vest demonstrators and anti-capitalists gathered in the French capital, putting security forces on high alert. More than 7,400 police were out on the streets with orders from Macron to take an "extremely firm stance" if faced with violence. French police have banned demonstrations on the Champs-Élysées Avenue, around the presidential palace in Paris and near the Notre Dame Cathedral, which was gutted by a devastating fire on April 15.

The clashes kicked off as crowds gathered on Montparnasse Boulevard, with hundreds of black-clad anarchists weaving their way to the front as thousands of unionists and yellow vests were quietly munching their lunch in the sun. Suddenly they pounced, hurling bottles and chunks of broken paving stones at the security forces, shouting: "Everyone hates the police!" During the protests, more than 330 people were reportedly arrested.

Paris has been scarred by looting, arson and violence during the past few months of yellow vest protests over economic grievances, and the French authorities are haunted by the serious violence that has broken out at May Day demonstrations in the past two years.

Macron last week tried to address the complaints of the yellow vest movement by announcing tax cuts for middle-class workers and an increase in pensions. But many yellow vest supporters consider the government's plans insufficient and want to keep the movement alive that started in November to oppose a fuel tax and quickly expanded into broad public rejections of Macron's economic policies.