A union representing Paris garbage workers announced another rolling strike is set to begin next week, just as piles of uncollected rubbish were disappearing from the streets of the capital.

A three-week stoppage by refuse collectors last month to protest pension reforms left the city strewn with 10,000 tonnes of rubbish, with some trash heaps rising to more than two metres (six feet) high.

The hard-left CGT, the largest public sector union, called on its members late Monday to begin another strike from Thursday April 13.

The industrial action is to demand "the withdrawal of the pension reforms", said a statement from the CGT's refuse workers branch.

It called on members to "to take part actively and in large numbers in the union and sector-specific days of action".

Refuse collectors can currently retire at 57, as long as they have the required number of years of social security contributions, but this would be increased to 59 under reforms being pushed through by President Emmanuel Macron.

Another national day of strikes and protests -- the 11th since the start of the year -- has been announced for Thursday, with unions and leftist opponents of the changes hoping to regain ebbing momentum.

All eyes are on France's constitutional court which is reviewing the pension legislation set to raise the minimum retirement age for most people from 62 to 64, bringing France more into line with its European neighbours.

The court will announce on April 14 whether the legislation is legally sound.

If it gives the go-ahead, Macron would be free to sign it into law, meaning it would enter force later this year.

The public sector garbage workers' strike is set to affect half of the French capital's districts -- the other half is managed by private companies.

But blockades of the city's three incinerator plants during last month's strike also affected private collections.

The CGT argues that the lower retirement age for sanitation workers -- refuse collectors and sewerage workers -- is justified because their life expectancy is between 12-17 years less than the average French person.