Uncollected rubbish clogged streets in France's capital Wednesday as unions made an 11th-hour bid to stop a deeply unpopular pensions reform from being passed.

Opinion polls show that around two-thirds of French people are against the legislation to raise the retirement age from 62 to 64, extend contributions for a full pension and scrap some special privileges for public sector employees.

But despite two months of protests and cross-sector strikes, the bill championed by President Emmanuel Macron appears on the verge of being pushed through parliament.

Several small demonstrations kicked off around France Wednesday morning, including in the northern city of Calais, on a new day of strikes and protests.

Police were expecting between 650,000 and 850,000 demonstrators nationwide, a source said on condition of anonymity, far fewer than the largest rallies last week.

Walkouts appeared more limited than in previous days of nationwide action, but workers in some sectors stood steadfast in rejecting the changes.

The most visible impact of the standoff so far has been piles of trash on Paris streets, where municipal garbage collectors and cleaners have stopped work since early last week.

Around 7,000 tons of black bin bags and cardboard boxes have accumulated on pavements and outside restaurants in around half the city, alarming foreign visitors.

Even in the other half of Paris, where private companies still whisk away refuse, collection has been complicated as two key incinerators outside the capital are on strike.

The street cleaners voted Tuesday to extend their walkout until next Monday, causing Interior Minister Gerald Darmanin to demand the capital's municipality order them back to work.

Paris mayor Anne Hidalgo retorted she had "no power" and no intention of doing so.