PARIS - Violent pension reform protests in France led to the postponement Friday of British King Charles III's trip to the country, highlighting the growing security and political problems faced by President Emmanuel Macron.

The French president condemned the latest burst of violence overnight, while a human rights watchdog criticized the 'excessive use of force' by police during recent demonstrations.

King Charles' first foreign trip as monarch had been intended to highlight warming Franco-British relations. Instead, it has underlined the severity of demonstrations engulfing Britain's neighbor just 10 months into Macron's second term.

Uproar over legislation to raise the retirement age from 62 to 64 years of age was enflamed when Macron exercised a controversial executive power to push the plan through parliament without a vote last week.

With fresh strikes expected Tuesday on what would have been the second day of the king's tour, Macron asked for the postponement of the royal visit, a British government spokesperson said.

The decision was made 'to welcome His Majesty King Charles III in conditions which reflect our friendly relations,' Macron's office said.

Police arrested more than 450 people Thursday, according to interior ministry figures.

In addition, 441 members of the security forces were injured on the most violent day of protests since the start of the year.

More than 900 fires were lit around Paris, with anarchist groups blamed for setting uncollected rubbish ablaze and smashing shop windows, leading to frequent clashes with riot police.

But rights groups, magistrates and left-wing politicians have also denounced alleged police brutality in recent days.

The Council of Europe -- the continent's leading human rights watchdog -- warned that sporadic acts of violence 'cannot justify excessive use of force by agents of the state' or 'deprive peaceful protesters of their right to freedom of assembly."

More than a million

More than a million people marched in France on Thursday, according to official estimates, as the protest movement was reinvigorated by Macron's refusal to back down over the past week.

In the northeast city of Rennes, regional officials denied claims by union leaders that police had deliberately targeted them with tear gas and a water cannon during Thursday's protests.

In Bordeaux, protesters set fire to the ancient wooden entrance to the city hall Thursday. King Charles had been set to visit the southwestern city Tuesday, after a day in Paris.

With protesters threatening to disrupt the royal visit and the streets of the capital strewn with rubbish because of a strike by waste collectors, some feel the trip's postponement will avoid further embarrassment for France.

Speaking to reporters during a trip to Brussels on Friday, Macron said discussions over rescheduling the visit could take place in the coming months.

'We have proposed that at the beginning of the summer, depending on our respective agendas, we can arrange a new state visit,' he said.

He also insisted that Paris 'would not give in to the violence.'

'I condemn the violence and offer my full support to the security forces who worked in an exemplary manner.'

Way out?

It remains unclear how the government will defuse a crisis that comes just four years after the 'Yellow Vest' demonstrations rocked the country.

'Everything depends on one man who is a prisoner of the political situation,' political scientist Bastien Francois from the Sorbonne University in Paris told AFP.

The leader of the moderate CFDT union, Laurent Berger, said Friday he had spoken to an aide to the president and suggested a pause on implementing the pensions law for six months while opening a channel for negotiations.

'It's the moment to say, 'Listen, let's put things on pause, let's wait six months,'' Berger told RTL radio. 'It would calm things down.'

While France's Constitutional Court still needs to give the final word on the reform, Macron said in a televised interview Wednesday that the changes needed to 'come into force by the end of the year.'

Blockades of oil refineries by striking workers continued on Friday, but the energy transition ministry said it had requisitioned enough workers to restart production at one of these and resume fuel supply to the capital.

About 15% of gas stations were still out of at least one fuel by Friday morning, according to an analysis of public data by AFP.

Some flights have been canceled until at least Wednesday at airports around the country due to a strike by air traffic controllers.

Police and protesters will face off again Saturday, and not just at demonstrations over the pension reform.

At Saint Solines, central France, thousands of people are expected at a protest against the deployment of new water-storage infrastructure for agricultural irrigation, despite an official ban on the gathering.