The heads of France's big energy companies urged individuals and businesses to limit power consumption immediately to prepare for a looming energy crisis.
In an open letter published by weekly newspaper Journal du Dimanche, the chief executives of Engie, EDF and Total said on Sunday: "We need to work collectively to reduce our consumption in order to regain room to manoeuvre."
The letter signed by Engie's Catherine MacGregor, EDF's Jean-Bernard Levy and TotalEnergies' Patrick Pouyanne cited sharp declines in Russian gas shipments as well as limited electricity generation because of maintenance issues.
Liquid gas supplies need to be restocked
This comes as French Prime Minister Elisabeth Borne said on Thursday that France aims to fill its gas storage facilities by early autumn.
The country's gas storage sites are 59% full at present.
Russia's invasion of Ukraine has thrown the spotlight on Europe's reliance on Russian gas, prompting a scramble to find alternative energy sources.
In March, French media reported that the government was in talks with TotalEnergies about boosting capacity to receive liquified natural gas (LNG) after the United States said it was prepared to increase deliveries to Europe.
Winter is coming
"Taking action as soon as this summer will allow us to be better prepared at the start of next winter, notably for preserving our gas reserves," the energy company executives said in their letter, adding that efforts to limit consumption should be "immediate, collective and massive".
They cited their own efforts to find new sources of gas and build a floating LNG terminal in the northern port of Le Havre.
France recently extended its mechanism for regulating gas prices to the end of the year.
Originally scheduled to run through to the end of June, the system is meant to limit the effects of soaring energy prices on cosumers' purchasing power.