The fourteenth day of protests will be held on June 6, the unions said, days before lawmakers debate a bill that would repeal the retirement changes forced through without a vote by Macron's ministers.

Police said almost 800,000 people turned out across France against the pension reform on Monday -- the Labour Day holiday -- while the hard-left CGT union tallied 2.3 million.

The unions said that while they would attend new discussions with cabinet ministers on issues ranging from boosting employment among older people to reforming vocational schools, they would "reiterate their refusal of the pensions reform".

"There is deep defiance and dialogue can only resume if the government shows it is finally willing to take the unions' positions into account," they added.

Nationwide 540 people were arrested during Monday's demonstrations, including 305 in Paris, Interior Minister Gerald Darmanin said.

The capital had seen "a level of violence in the vanguard of the march... that far exceeded" previous demonstrations, Paris police chief Laurent Nunez told broadcaster France Info, blaming "hooligans".

Darmanin said three officers were "in an extremely difficult situation" although not fighting for their lives.

One policeman was in hospital with burns to his face after being struck by a Molotov cocktail.

While there was no official figure for the number of demonstrators hurt as police used tear gas, riot grenades and other weapons, at least two journalists, including an AFP photographer, reported being hit without serious injuries.