French President Emmanuel Macron signed his controversial pension reform into law Saturday, raising the state pension age, despite mass three months of protests and pleas from unions not to implement the legislation.

The proclamation of the law came after France's Constitutional Council on Friday approved the main pension-age increase and follows months of demonstrations against the plan, which the government forced through parliament without a final vote.

The legislation, which will progressively push up the age for drawing a state pension to 64 from 62, is deeply unpopular and protests immediately broke out when the Constitutional Council's decision was announced.

Crowds marched through Paris on Friday evening, with some burning trash bins, while in the northwestern city of Rennes the entrance to a police station was set on fire.

Trade unions on Friday called on the government not to enact the legislation, despite the green light from the Constitutional Council, and urged workers to turn out in force for marches on Labour Day on May 1.

They rejected an invitation by Macron to meet on Tuesday.

The president has staked his reputation as a reformer on the pension changes, which he says are needed to avoid billions of euros of deficit each year by the end of the decade.

"Never give up, that's my motto," he said on Friday before the Constitutional Council verdict, as he visited Notre-Dame on the anniversary of a fire that gutted the celebrated Paris cathedral.

The government plans to apply the new legislation from Sept. 1.

Francois Ruffin, a lawmaker from the left-wing LFI party, on Twitter accused the government of proclaiming the pension law "like thieves in the night."

Opposition parties have tabled another bid for a citizens' referendum on the reform after the Constitutional Council on Friday rejected a first such proposal.

The pension system is a cornerstone of France's cherished social protection model and trade unions say extra funding can be found elsewhere, including by taxing the rich more heavily.

Public hostility to the reform has increased since the government, which does not have a majority in parliament, pushed through the bill in March without a final vote using special constitutional powers.