Workers at the site in Gournay-sur-Aronde, located 93 km north of Paris, say they are striking to demand higher wages amid soaring global inflation. Industrial action is gaining momentum across France's energy sector just as President Emmanuel Macron and his European counterparts tackle a gas crisis that is prompting concerns over winter supplies.

Earlier Thursday France's FNME-CGT union made a call to all workers in the country's energy sector to stage "a powerful strike", including blockades of facilities, on July 4.

French gas utility Engie, which operates the Gournay gas storage facility, told Reuters that "it is undergoing long-planned maintenance. Operations will resume in the coming days." It did not respond directly to questions on reports of a work stoppage.

Gournay is operated by Engie subsidiary, Storengy.

The company remained on track to fill its storage tanks ahead of the winter by Nov. 1st, Engie said.

(Reporting by Benjamin Mallet; Editing by Richard Lough and Aurora Ellis)