(Adds Total comment on Grandpuits situation)
PARIS, Nov 23 (Reuters) - Oil industry workers were on strike for a third day on Friday at four of France's seven refineries and unions urged employees to step up blockades to force the plants to halt production.
Support for continued action came after unions rejected on Thursday a 1.5 percent salary increase offer by oil industry federation UFIP, saying it was below the French inflation rate.
A spokesman for UFIP said talks to resolve the dispute had ended late on Thursday without agreement.
The CGT and fellow hard-left union FO have called on striking workers to step up blockades of refineries and fuel depots so companies are faced with supply shortages.
Thierry Defresne of the CGT union told Reuters that Total's Grandpuits refinery south of Paris, one of the refineries where workers remain on strike, was completely blocked and only had enough crude to continue functioning until Sunday midday.
But a Total spokeswoman said France's CIM oil storage and dispatch services company, which supplies crude to refineries operated by Total and Exxon, was working normally.
"Total denies the fact that the Grandpuits refinery will run out of crude, forcing a shutdown," she said, although she said outbound of deliveries of fuel from Grandpuits were blocked.
Some CIM employees staged a brief walk out on Thursday in solidarity with the striking refinery workers but they resumed work later in the day.
The Total spokeswoman said deliveries of fuel the firm's Donges refinery on the west coast had resumed, while she said only one of Total's fuel depots, La Mede in the south, was blocked.
Workers at Donges refinery and at Exxon Mobil Corp's Fos-sur-Mer refinery in the south voted to suspend their strike action pending salary talks, the CGT's Defresne said.
He said workers were still striking at Total's Grandpuits, Gonfreville and Feyzin refineries, along with Ineos' Lavera refinery.
The strike over pay and bonuses adds to challenges facing fuel companies, which are also facing protests from the "yellow vest" movement of citizens who oppose higher fuel taxes and have sporadically blockaded oil depots this week.
UFIP said some petrol stations were experiencing minor supply issues but there were no widespread fuel shortages. (Reporting by Gus Trompiz and Bate Felix; Editing by Richard Lough and Edmund Blair)