PARIS - FRANCE'S massive strikes opposing changes in the country's pension system showed some signs of weakening on Monday when Marseille garbage collectors and workers at three oil refineries voted to end their walkouts.

But the French finance minister announced that the strikes are costing the national economy up to 400 million euros (S$721 million) each day, as workers continued to block other oil refineries and some trash incinerators to protest the plan to raise the retirement age to 62.

Rotting piles of garbage - now at nearly 9,000 tons - are becoming a health hazard in Marseille, and trash collectors there explained their decision on Monday to suspend their 2-week- long walkout as a response to the mounting hygiene problems in the Mediterranean city.

'There's not a wide health risk on the city, but we have noticed a worsening of hygiene and security problems,' the head of the FO-Territoriaux union said at a news conference. 'We're a responsible union.'

Twelve striking refineries had been shut down for nearly two weeks, but their protest movement appeared to weaken on Monday after workers at three refineries voted to end their walkout. The French oil refineries' body, UFIP, said all the country's oil depots had also been unblocked.

The oil workers' return to work is likely to ease the ongoing gasoline shortages, which on Monday still had about one in four gas stations in France shuttered. President Nicolas Sarkozy has stood firm throughout the weeks long protest movement, insisting the reform is necessary to save the money-losing retirement system and ensure funds for future generations as life expectancy increases and the nation's debt soars.

Strikes cost up to $721m a day